def fit(self, X, y=None, **fit_params):
        """
        This method performs preliminary computations in order to set up the
        figure or perform other analyses. It can also call drawing methods in
        order to set up various non-instance related figure elements.

        This method must return self.
        """

        # Handle the feature names if they're None.
        if self.features_ is None:

            # If X is a data frame, get the columns off it.
            if is_dataframe(X):
                self.features_ = np.array(X.columns)

            # Otherwise create numeric labels for each column.
            else:
                _, ncols = X.shape
                self.features_ = np.arange(0, ncols)

        return self
This method performs preliminary computations in order to set up the
        figure or perform other analyses. It can also call drawing methods in
        order to set up various non-instance related figure elements.

        This method must return self.