@staticmethod
def get_count(df, col_id):
    """
        Count the unique ids in col_id of df
        ------------
        :param df: encoded pandas Dataframe
        :param col_id: name of the column in df
        :return count: number of different values in col_id of df
        """
    list_unique_id = df[[col_id]].groupby(col_id, as_index=False)
    count = list_unique_id.size()
    return count
