`chain.get_graph()` doesn't play nicely with  `chain.map()` or `list[str]`
Labels: name: auto:bug

### System Info

Langchain 0.1.0
python 3.10

### Who can help?

@agola11 

### Information

- [ ] The official example notebooks/scripts
- [X] My own modified scripts

### Related Components

- [ ] LLMs/Chat Models
- [ ] Embedding Models
- [ ] Prompts / Prompt Templates / Prompt Selectors
- [ ] Output Parsers
- [ ] Document Loaders
- [ ] Vector Stores / Retrievers
- [ ] Memory
- [ ] Agents / Agent Executors
- [ ] Tools / Toolkits
- [X] Chains
- [X] Callbacks/Tracing
- [ ] Async

### Reproduction

reproducing the error could be as follows

```python 
...
#################################################################
## get multiple queries to be searched on the web

query_generation_chain = (
    search_queries_prompt
    | llm.bind(stop=TOGETHER_STOP_KEYWORDS)
    | CommaSeparatedListOutputParser()
)


#################################################################
## scrape and summarize a webpages based on urls


summarize_chain = RunnablePassthrough.assign(
    summary=RunnablePassthrough.assign(text=lambda x: scrape_webpage(x["url"])[:10_000])
    | summarize_prompt
    | llm
    | StrOutputParser(),
)   | (lambda x: f'URL: {x["url"]} \n\nSUMMARY: {x["summary"]}')

chain = (
    RunnablePassthrough.assign(urls = query_generation_chain | fetch_links_from_web)
    | RunnableLambda(lambda x: [{"question": x["question"], "url": url} for url in x["urls"]])
    | summarize_chain.map()  ## generate list of summarized article for each link
    | (lambda reports: "\n\n".join(reports))  ## combine the summaries into a report
)
```
if i  invoke `get_graph()` on the chain like this :
```python 
chain.get_graph()
```
i get this error :
```console
Traceback (most recent call last):
  File "/home/joede/dev/llm_playground/researcher/main.py", line 30, in <module>
    report_writer_chain.get_graph().print_ascii()
  File "/home/joede/.cache/pypoetry/virtualenvs/researcher-Jp5_VGHR-py3.10/lib/python3.10/site-packages/langchain_core/runnables/base.py", line 1690, in get_graph
    step_graph = step.get_graph(config)
  File "/home/joede/.cache/pypoetry/virtualenvs/researcher-Jp5_VGHR-py3.10/lib/python3.10/site-packages/langchain_core/runnables/passthrough.py", line 379, in get_graph
    graph = self.mapper.get_graph(config)
  File "/home/joede/.cache/pypoetry/virtualenvs/researcher-Jp5_VGHR-py3.10/lib/python3.10/site-packages/langchain_core/runnables/base.py", line 2282, in get_graph
    step_graph = step.get_graph()
  File "/home/joede/.cache/pypoetry/virtualenvs/researcher-Jp5_VGHR-py3.10/lib/python3.10/site-packages/langchain_core/runnables/passthrough.py", line 379, in get_graph
    graph = self.mapper.get_graph(config)
  File "/home/joede/.cache/pypoetry/virtualenvs/researcher-Jp5_VGHR-py3.10/lib/python3.10/site-packages/langchain_core/runnables/base.py", line 2282, in get_graph
    step_graph = step.get_graph()
  File "/home/joede/.cache/pypoetry/virtualenvs/researcher-Jp5_VGHR-py3.10/lib/python3.10/site-packages/langchain_core/runnables/base.py", line 1690, in get_graph
    step_graph = step.get_graph(config)
  File "/home/joede/.cache/pypoetry/virtualenvs/researcher-Jp5_VGHR-py3.10/lib/python3.10/site-packages/langchain_core/runnables/base.py", line 2906, in get_graph
    graph = super().get_graph(config)
  File "/home/joede/.cache/pypoetry/virtualenvs/researcher-Jp5_VGHR-py3.10/lib/python3.10/site-packages/langchain_core/runnables/base.py", line 399, in get_graph
    output_node = graph.add_node(self.get_output_schema(config))
  File "/home/joede/.cache/pypoetry/virtualenvs/researcher-Jp5_VGHR-py3.10/lib/python3.10/site-packages/langchain_core/runnables/base.py", line 331, in get_output_schema
    if inspect.isclass(root_type) and issubclass(root_type, BaseModel):
  File "/usr/lib/python3.10/abc.py", line 123, in __subclasscheck__
    return _abc_subclasscheck(cls, subclass)
TypeError: issubclass() arg 1 must be a class
```
with further inspection i found it error when it gets here:
```python
def get_input_schema(...):
    ....
    root_type = self.OutputType
      if inspect.isclass(root_type) and issubclass(root_type, BaseModel):
         return root_type
```
in the `langchain_core/runnable/base.py`       


### Expected behavior

the expected output should be a graph of ascii characters  that should look like this :
```console
  +---------------------------------+                                 
                                        | Parallel<research_summary>Input |                                 
                                        +---------------------------------+                                 
                                               ****                        *******                          
                                            ***                                   *******                   
                                          **                                             ******             
                           +---------------------+                                             ****         
                           | Parallel<urls>Input |                                                *         
                           +---------------------+                                                *         
                           ***                  ****                                              *         
                       ****                         ***                                           *         
                     **                                ****                                       *         
      +--------------------+                               **                                     *         
      | ChatPromptTemplate |                                *                                     *         
      +--------------------+                                *                                     *         
                 *                                          *                                     *         
                 *                                          *                                     *         
                 *                                          *                                     *         
        +---------------+                                   *                                     *         
        | WithFallbacks |                                   *                                     *         
        +---------------+                                   *                                     *         
                 *                                          *                                     *         
                 *                                          *                                     *         
                 *                                          *                                     *         
+--------------------------------+                          *                                     *         
| CommaSeparatedListOutputParser |                          *                                     *         
+--------------------------------+                          *                                     *         
                 *                                          *                                     *         
                 *                                          *                                     *         
                 *                                          *                                     *         
 +------------------------------+                    +-------------+                              *         
 | Lambda(fetch_links_from_web) |                    | Passthrough |                              *         
 +------------------------------+                   *+-------------+                              *         
                           ***                  ****                                              *         
                              ****          ****                                                  *         
                                  **      **                                                      *         
                           +----------------------+                                        +-------------+  
                           | Parallel<urls>Output |                                      **| Passthrough |  
                           +----------------------+                               *******  +-------------+  
                                               ****                         ******                          
                                                   ***               *******                                
                                                      **         ****                                       
                                        +----------------------------------+                                
                                        | Parallel<research_summary>Output |                                
                                        +----------------------------------+                                
                                                          *                                                 
                                                          *                                                 
                                                          *                                                 
                                               +--------------------+                                       
                                               | ChatPromptTemplate |                                       
                                               +--------------------+                                       
                                                          *                                                 
                                                          *                                                 
                                                          *                                                 
                                                 +---------------+                                          
                                                 | WithFallbacks |                                          
                                                 +---------------+                                          
                                                          *                                                 
                                                          *                                                 
                                                          *                                                 
                                                +-----------------+                                         
                                                | StrOutputParser |                                         
                                                +-----------------+                                         
                                                          *                                                 
                                                          *                                                 
                                                          *                                                 
                                             +-----------------------+                                      
                                             | StrOutputParserOutput |                                      
                                             +-----------------------+    
```