def register_regex_entity(self, regex_str):
if regex_str and regex_str not in self._regex_strings:<EOL><INDENT>self._regex_strings.add(regex_str)<EOL>self.regular_expressions_entities.append(re.compile(regex_str, re.IGNORECASE))<EOL><DEDENT>
A regular expression making use of python named group expressions.

Example: (?P<Artist>.*)

regex_str(str): a string representing a regular expression as defined above