@classmethod<EOL><INDENT>def is_key(cls, key_string: str) -> bool:<DEDENT>
<EOL>lowered_key_string = key_string.lower()<EOL>try:<EOL><INDENT>cls(lowered_key_string)<EOL><DEDENT>except ValueError:<EOL><INDENT>return _code_point_re.fullmatch(lowered_key_string) is not None<EOL><DEDENT>else:<EOL><INDENT>return True<EOL><DEDENT>
Returns if a string represents a key.