code: def get_tokens(self, token_attrib='token', token_strings_only=False):
          
          if token_strings_only:
              for token_id in self.tokens:
                  yield self.get_token(token_id, token_attrib)
          else:
              for token_id in self.tokens:
                  yield (token_id, self.get_token(token_id, token_attrib))
docs: returns a list of (token node ID, token) which represent the tokens
          of the input document (in the order they occur).
  
          Parameters
          ----------
          token_attrib : str
              name of the node attribute that contains the token string as its
              value (default: token).
  
          Yields
          -------
          result : generator of (str, unicode) or generator unicode
              a generator of (token node ID, token string) tuples if
              token_strings_only==False, a generator of token strings otherwise