Return the math word groups for a language code.
    The language_code should be an ISO 639-2 language code.
    https://www.loc.gov/standards/iso639-2/php/code_list.php

def word_groups_for_language(language_code):
    """
    Return the math word groups for a language code.
    The language_code should be an ISO 639-2 language code.
    https://www.loc.gov/standards/iso639-2/php/code_list.php
    """

    if language_code not in LANGUAGE_CODES:
        message = '{} is not an available language code'.format(language_code)
        raise InvalidLanguageCodeException(message)

    return MATH_WORDS[language_code]