message: added mention that _optimal matching should be removed at some point
diff: @@ -44,6 +44,9 @@ def _optimal_matching(X, Y, withcost=False):
  if i >= len(X) or j >= len(Y), it means they
  represent the diagonal.
  They will be encoded by -1 afterwards.
  +
  + NOTE : this code will be removed for final merge,
  + and wasserstein.optimal_matching will be used instead.
  '''
  n = len(X)
  