def pop(self, key, default=_marker):
try:<EOL><INDENT>popped = self[key]<EOL>del self[key]<EOL>return popped<EOL><DEDENT>except KeyError:<EOL><INDENT>if default == _marker:<EOL><INDENT>raise<EOL><DEDENT>return default<EOL><DEDENT>
remove the item by key
        If not default is specified, raise KeyError if nothing
        could be removed.
        Return 'default' if specified and nothing could be removed