def key_occurrence(self, key, update=True):
if update:<EOL><INDENT>self.update()<EOL><DEDENT>result = {}<EOL>for k, v in self.database.items():<EOL><INDENT>if key in v:<EOL><INDENT>result[str(v[key])] = k<EOL><DEDENT><DEDENT>return result<EOL>
Return a dict containing the value of the provided key and its uuid as
value.