Make sure that spacy and neuralcoref are installed in your current Python environment. Follow directions at:

    https://github.com/huggingface/neuralcoref

Note: the neuralcoref library is outdated and only can be installed with the older version of spaCy 2.1

pip install -U pip setuptools wheel pip install -U 'spacy[apple]' python -m spacy download en_core_web_sm