In a python based, node graph UI called ComfyUI, I am getting the following error:

```
!!! Exception during processing!!! Sorry, GeneratorExp is not available in this evaluator
Traceback (most recent call last):
  File "D:\AI Generation\Software\ComfyUI_windows_portable\python_embeded\Lib\site-packages\simpleeval.py", line 434, in _eval
    handler = self.nodes[type(node)]
              ~~~~~~~~~~^^^^^^^^^^^^
KeyError: <class 'ast.GeneratorExp'>

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "D:\AI Generation\Software\ComfyUI_windows_portable\ComfyUI\execution.py", line 151, in recursive_execute
    output_data, output_ui = get_output_data(obj, input_data_all)
                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "D:\AI Generation\Software\ComfyUI_windows_portable\ComfyUI\execution.py", line 81, in get_output_data
    return_values = map_node_over_list(obj, input_data_all, obj.FUNCTION, allow_interrupt=True)
                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "D:\AI Generation\Software\ComfyUI_windows_portable\ComfyUI\execution.py", line 74, in map_node_over_list
    results.append(getattr(obj, func)(**slice_dict(input_data_all, i)))
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "D:\AI Generation\Software\ComfyUI_windows_portable\ComfyUI\custom_nodes\efficiency-nodes-comfyui\efficiency_nodes.py", line 4406, in evaluate
    result = simpleeval.simple_eval(python_expression, names=variables, functions=functions)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "D:\AI Generation\Software\ComfyUI_windows_portable\python_embeded\Lib\site-packages\simpleeval.py", line 748, in simple_eval
    return s.eval(expr)
           ^^^^^^^^^^^^
  File "D:\AI Generation\Software\ComfyUI_windows_portable\python_embeded\Lib\site-packages\simpleeval.py", line 428, in eval
    return self._eval(previously_parsed or self.parse(expr))
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "D:\AI Generation\Software\ComfyUI_windows_portable\python_embeded\Lib\site-packages\simpleeval.py", line 440, in _eval
    return handler(node)
           ^^^^^^^^^^^^^
  File "D:\AI Generation\Software\ComfyUI_windows_portable\python_embeded\Lib\site-packages\simpleeval.py", line 443, in _eval_expr
    return self._eval(node.value)
           ^^^^^^^^^^^^^^^^^^^^^^
  File "D:\AI Generation\Software\ComfyUI_windows_portable\python_embeded\Lib\site-packages\simpleeval.py", line 440, in _eval
    return handler(node)
           ^^^^^^^^^^^^^
  File "D:\AI Generation\Software\ComfyUI_windows_portable\python_embeded\Lib\site-packages\simpleeval.py", line 495, in _eval_binop
    return operator(self._eval(node.left), self._eval(node.right))
                    ^^^^^^^^^^^^^^^^^^^^^
  File "D:\AI Generation\Software\ComfyUI_windows_portable\python_embeded\Lib\site-packages\simpleeval.py", line 440, in _eval
    return handler(node)
           ^^^^^^^^^^^^^
  File "D:\AI Generation\Software\ComfyUI_windows_portable\python_embeded\Lib\site-packages\simpleeval.py", line 495, in _eval_binop
    return operator(self._eval(node.left), self._eval(node.right))
                                           ^^^^^^^^^^^^^^^^^^^^^^
  File "D:\AI Generation\Software\ComfyUI_windows_portable\python_embeded\Lib\site-packages\simpleeval.py", line 440, in _eval
    return handler(node)
           ^^^^^^^^^^^^^
  File "D:\AI Generation\Software\ComfyUI_windows_portable\python_embeded\Lib\site-packages\simpleeval.py", line 539, in _eval_call
    return func(
           ^^^^^
  File "D:\AI Generation\Software\ComfyUI_windows_portable\python_embeded\Lib\site-packages\simpleeval.py", line 540, in <genexpr>
    *(self._eval(a) for a in node.args), **dict(self._eval(k) for k in node.keywords)
      ^^^^^^^^^^^^^
  File "D:\AI Generation\Software\ComfyUI_windows_portable\python_embeded\Lib\site-packages\simpleeval.py", line 436, in _eval
    raise FeatureNotAvailable(
simpleeval.FeatureNotAvailable: Sorry, GeneratorExp is not available in this evaluator
```

It is when I used a node called Evaluate Strings, which takes in three string variables, a, b and c, and let's me define a python expression, and it outputs the resulting string from this python expression, I have defined the inputs and python expression as follows:

a = "seveneleven, konbini, scenery, storefront, japan,"
b = "scenery, storefront, seveneleven, konbini, japan, outdoors, shop, convenience store, road, sign, building, real world location, street, ground vehicle, sky, city, day, motor vehicle, lamppost, power lines"
c = ""
python_expression = "'{1-5$$, $$' + '|'.join(token for token in re.split(r'\s*,\s*', b) if token not in re.split(r'\s*,\s*', a)) + '}'"

(Python expression is represented as a string, which is why I put it in "", however it executes it as a python statement, rather than treating it as a string)

What might be the problem and how could I potentially resolve it?