def fit_from_df(self, df):
    (y, x) = convert_df_to_yx(df, self.xheader, self.yheader)
    return self.fit(x, y)
def fit_from_df(self, df):
    (y, x) = convert_df_to_yx(df, self.xheader, self.yheader)
    return self.fit(x, y)