class_docstr: Object for core-components (POS, Dependency Relations, etc).
  
  Attributes:
      _doc_text: the doc text
      _sentences: list of sentences, each word in a sentence is
          represented by a dictionary, structured as follows: {'start': (int), 'len': (int),
          'pos': (str), 'ner': (str), 'lemma': (str), 'gov': (int), 'rel': (str)}
code: def __init__(self, doc_text: str = "", sentences: list = None):
      if sentences is None:
          sentences = []
      self._doc_text = doc_text
      self._sentences = sentences
  
imports: import json
  from nlp_architect.utils.io import validate
label_desc: Use image node_id 1 to create a new CoreNLPDoc object  with example: obj = CoreNLPDoc(doc_text, sentences)