code: def fit(self, sequences, y=None):
          
          check_iter_of_sequences(sequences)
          s = super(MultiSequencePreprocessingMixin, self)
          s.fit(self._concat(sequences))
  
          return self
docs: Fit Preprocessing to X.
  
          Parameters
          ----------
          sequences : list of array-like, each of shape [sequence_length, n_features]
              A list of multivariate timeseries. Each sequence may have
              a different length, but they all must have the same number
              of features.
          y : None
              Ignored
  
          Returns
          -------
          self