def base64url_decode(input):
rem = len(input) % <NUM_LIT:4><EOL>if rem > <NUM_LIT:0>:<EOL><INDENT>input += b'<STR_LIT:=>' * (<NUM_LIT:4> - rem)<EOL><DEDENT>return base64.urlsafe_b64decode(input)<EOL>
Helper method to base64url_decode a string.

    Args:
        input (str): A base64url_encoded string to decode.