@staticmethod
def _is_intrinsic(function):
    """Returns True if the provided function is a Tosca get_artifact function.

        Examples:

        * "{ concat: ['str1', 'str2'] }"
        * "{ token: [ <string_with_tokens>, <string_of_token_chars>, <substring_index> ] }"

        :param function: Function as string.
        :return: True if function is a Tosca get_artifact function, otherwise False.
        """
    if isinstance(function, dict) and len(function) == 1:
        func_name = list(function.keys())[0]
        return func_name in ['concat', 'token']
    return False
