>>> doc = nlp('The cat sat on the mat')
>>> for np in doc.noun_chunks:
        np.merge(np.root.tag_, np.text, np.root.ent_type_)

---------------------------------------------------------------------------
IndexError                                Traceback (most recent call last)
<ipython-input-409-f6294d1a1cf8> in <module>()
      1 doc = nlp('The cat sat on the mat')
----> 2 for np in doc.noun_chunks:
      3     np.merge(np.root.tag_, np.text, np.root.ent_type_)

/Users/yaser/miniconda3/envs/spacy/lib/python3.5/site-packages/spacy/tokens/doc.pyx in noun_chunks (spacy/tokens/doc.cpp:7745)()

/Users/yaser/miniconda3/envs/spacy/python3.5/site-packages/spacy/syntax/iterators.pyx in english_noun_chunks (spacy/syntax/iterators.cpp:1559)()

/Users/yaser/miniconda3/envs/spacy/lib/python3.5/site-packages/spacy/tokens/doc.pyx in spacy.tokens.doc.Doc.__getitem__ (spacy/tokens/doc.cpp:4853)()

IndexError: list index out of range