@classmethod
def _expand_row_data(cls, datum: dict, column: str, column_hierarchy: dict
    ) ->None:
    """
        Separate out nested fields and its value in a row of data
        :param datum: row of data
        :param column: row column name
        :param column_hierarchy: dictionary tracking structural columns and its
               nested fields
        """
    if column in datum:
        row_data = datum[column]
        row_children = column_hierarchy[column]['children']
        if row_data and len(row_data) != len(row_children):
            raise Exception(
                'The number of data values and number of nestedfields are not equal'
                )
        elif row_data:
            for index, data_value in enumerate(row_data):
                datum[row_children[index]] = data_value
        else:
            for row_child in row_children:
                datum[row_child] = ''
