code: def _len_lcs(x, y):
      """
      Returns the length of the Longest Common Subsequence between sequences x
      and y.
      Source: http://www.algorithmist.com/index.php/Longest_Common_Subsequence
  
      :param x: sequence of words
      :param y: sequence of words
      :returns integer: Length of LCS between x and y
      """
      table = _lcs(x, y)
      n, m = _get_index_of_lcs(x, y)
      return table[n, m]
  
file_path: sumy/sumy/evaluation/rouge.py
imports: from __future__ import absolute_import
  from __future__ import division, print_function, unicode_literals
  from ..models.dom import Sentence
label_desc: Use image node_id 5 for calling a global function with example usage: _len_lcs(x, y) and returns: table