@classmethod<EOL><INDENT>def _check_source(cls, source_file_hash, source):<DEDENT>
embedding_name = cls.__name__.lower()<EOL>if source not in source_file_hash:<EOL><INDENT>raise KeyError('<STR_LIT>'<EOL>'<STR_LIT>'.format(<EOL>source, embedding_name, embedding_name,<EOL>'<STR_LIT:U+002CU+0020>'.join(source_file_hash.keys())))<EOL><DEDENT>
Checks if a pre-trained token embedding source name is valid.


        Parameters
        ----------
        source : str
            The pre-trained token embedding source.