code: def is_docstring(tokens, previous_logical):
      
      for token_type, text, start, _, _ in tokens:
          if token_type == tokenize.STRING:
              break
          elif token_type != tokenize.INDENT:
              return False
      else:
          return False
      line = text.lstrip()
      start, start_triple = _find_first_of(line, START_DOCSTRING_TRIPLE)
      if (previous_logical.startswith("def ") or
              previous_logical.startswith("class ")):
          if start == 0:
              return text
docs: Return found docstring
  
      'A docstring is a string literal that occurs as the first statement in a
      module, function, class,'
      http://www.python.org/dev/peps/pep-0257/#what-is-a-docstring