def canon(raw_attr_name: str) -> str:
if raw_attr_name:  <EOL><INDENT>return raw_attr_name.replace('<STR_LIT:U+0020>', '<STR_LIT>').lower()<EOL><DEDENT>return raw_attr_name<EOL>
Canonicalize input attribute name as it appears in proofs and credential offers: strip out
white space and convert to lower case.

:param raw_attr_name: attribute name
:return: canonicalized attribute name