So apparently writing a function like
```python
def _run_pool(n_jobs, fixed_vocab, raw_documents, chunk_size, analyze, vocab):
    pool = Pool(processes=n_jobs)
    if not fixed_vocab:
        result = pool.map(_count_new_vocab, 
                          _chunk_docs(raw_documents, chunk_size, 
                          analyze, vocab=None))
```
and calling it from the class doesn't work either.