docs: def levenshtein(s, t):
      """ Compute the Levenshtein distance between 2 strings, which
      is the minimum number of operations required to perform on a string to
      get another one.
  
      code taken from https://en.wikibooks.org
  
      :param basestring s:
      :param basestring t:
      :rtype: int
      """
      ''' From Wikipedia article; Iterative with two matrix rows. '''
      if s == t:
          return 0
      elif len(s) == 0:
          return len(t)
      elif len(t) == 0:
          return len(s)
      v0 = [None] * (len(t) + 1)
      v1 = [None] * (len(t) + 1)
      for i in range(len(v0)):
          v0[i] = i
      for i in range(len(s)):
          v1[0] = i + 1
          for j in range(len(t)):
              cost = 0 if s[i] == t[j] else 1
              v1[j + 1] = min(v1[j] + 1, v0[j + 1] + 1, v0[j] + cost)
          for j in range(len(v0)):
              v0[j] = v1[j]
  
      return v1[len(t)]