Templatetagish wrapper for Translator.transchoice()

def tranz_context(parser, token):
    """
    Templatetagish wrapper for Translator.transchoice()
    """
    tokens = token.split_contents()

    parameters = {}
    for idx, token in enumerate(tokens[1:], start=1):
        if "=" in token:
            if token[0:token.index('=')] not in ("domain", "prefix", "locale"):
                raise TemplateSyntaxError(
                    "Unexpected token {0} in tag {{tag_name}}".format(token)
                )

            k, v = token[0:token.index('=')], token[token.index('=') + 1:]
            parameters[k] = v
        else:
            raise TemplateSyntaxError(
                "Unexpected token {0} in tag {{tag_name}}".format(token))

    return TranzContextNode(
        parameters.get('prefix', None),
        parameters.get('domain', None),
        parameters.get('locale', None)
    )