def generate_header_list(unsorted_keys):
    """Return a list of headers for the CSV file, ensuing that the order of the
    first four headers is fixed and the remainder are sorted."""

    unsorted_keys.remove('identifier')

    sorted_remainder = sorted(unsorted_keys)

    header_list = ['identifier', 'label1', 'label2', 'label3']
    header_list += sorted_remainder

    return header_list