code: def _len_lcs(x, y):
    
    table = _lcs(x, y)
    n, m = len(x), len(y)
    return table[n, m]
docs: Returns the length of the Longest Common Subsequence between two seqs.
  
    Source: http://www.algorithmist.com/index.php/Longest_Common_Subsequence
  
    Args:
      x: sequence of words
      y: sequence of words
  
    Returns
      integer: Length of LCS between x and y