def get_value(input_data, field_name, required=False):
    """
    Return an unencoded value from an MMTF data structure.

    :param input_data:
    :param field_name:
    :param required:
    :return:
    """
    if field_name in input_data:
        return input_data[field_name]
    elif required:
        raise Exception('ERROR: Invalid MMTF File, field: {} is missing!'.format(field_name))
    else:
        return None