code: def _modelmat(self, X, term=-1):
          
          X = check_X(X, n_feats=self.statistics_['m_features'],
                      edge_knots=self.edge_knots_, dtypes=self.dtype,
                      features=self.feature, verbose=self.verbose)
  
          return self.terms.build_columns(X, term=term)
docs: Builds a model matrix, B, out of the spline basis for each feature
  
          B = [B_0, B_1, ..., B_p]
  
          Parameters
          ---------
          X : array-like of shape (n_samples, m_features)
              containing the input dataset
          term : int, optional
              term index for which to compute the model matrix
              if -1, will create the model matrix for all features
  
          Returns
          -------
          modelmat : sparse matrix of len n_samples
              containing model matrix of the spline basis for selected features