def serialized(self):
        to_ret = {}
        for group, requirements in self.items():
            to_ret[group] = [str(requirement) for requirement in requirements]
        return to_ret
def find_many_example_files(
        top_directory_name, shuffled=True, first_spc_date_string=None,
        last_spc_date_string=None, first_batch_number=None,
        last_batch_number=None, raise_error_if_any_missing=True):
    """Looks for many files with input examples.

    :param top_directory_name: See doc for `find_example_file`.
    :param shuffled: Same.
    :param first_spc_date_string: [used only if `shuffled = False`]
        First SPC date (format "yyyymmdd").  This method will look for all SPC
        dates from `first_spc_date_string`...`last_spc_date_string`.
    :param last_spc_date_string: See above.
    :param first_batch_number: [used only if `shuffled = True`]
        First batch number (integer).  This method will look for all batches
        from `first_batch_number`...`last_batch_number`.
    :param last_batch_number: See above.
    :param raise_error_if_any_missing: Boolean flag.  If *any* desired file is
        not found and `raise_error_if_any_missing = True`, this method will
        error out.
    :return: example_file_names: 1-D list of paths to example files.
    :raises: ValueError: if no files are found.
    """

    error_checking.assert_is_boolean(shuffled)

    if shuffled:
        error_checking.assert_is_integer(first_batch_number)
        error_checking.assert_is_integer(last_batch_number)
        error_checking.assert_is_geq(first_batch_number, 0)
        error_checking.assert_is_geq(last_batch_number, first_batch_number)

        example_file_pattern = (
            '{0:s}/batches{1:s}-{1:s}/input_examples_batch{1:s}.nc'
        ).format(top_directory_name, BATCH_NUMBER_REGEX)

        example_file_names = glob.glob(example_file_pattern)

        if len(example_file_names) > 0:
            batch_numbers = numpy.array(
                [_file_name_to_batch_number(f) for f in example_file_names],
                dtype=int)
            good_indices = numpy.where(numpy.logical_and(
                batch_numbers >= first_batch_number,
                batch_numbers <= last_batch_number
            ))[0]

            example_file_names = [example_file_names[k] for k in good_indices]

        if len(example_file_names) == 0:
            error_string = (
                'Cannot find any files with batch number from {0:d}...{1:d}.'
            ).format(first_batch_number, last_batch_number)
            raise ValueError(error_string)

        return example_file_names

    spc_date_strings = time_conversion.get_spc_dates_in_range(
        first_spc_date_string=first_spc_date_string,
        last_spc_date_string=last_spc_date_string)

    example_file_names = []
    for this_spc_date_string in spc_date_strings:
        this_file_name = find_example_file(
            top_directory_name=top_directory_name, shuffled=False,
            spc_date_string=this_spc_date_string,
            raise_error_if_missing=raise_error_if_any_missing)

        if not os.path.isfile(this_file_name):
            continue
        example_file_names.append(this_file_name)

    if len(example_file_names) == 0:
        error_string = (
            'Cannot find any file with SPC date from {0:s} to {1:s}.'
        ).format(first_spc_date_string, last_spc_date_string)

        raise ValueError(error_string)

    return example_file_names