def if_match(self):
match = True<EOL>if_match = self.request.META.get('<STR_LIT>')<EOL>if if_match:<EOL><INDENT>etag = self.etag()<EOL>if etag != if_match:<EOL><INDENT>match = False<EOL><DEDENT><DEDENT>return match<EOL>
Optimistic concurrency control.