def frame(self, min_x=None, min_y=None, max_x=None, max_y=None):
ret = self.line_ending.join(self.rows(min_x, min_y, max_x, max_y))<EOL>if IS_PY3:<EOL><INDENT>return ret<EOL><DEDENT>return ret.encode('<STR_LIT:utf-8>')<EOL>
String representation of the current :class:`Canvas` object pixels.

        :param min_x: (optional) minimum x coordinate of the canvas
        :param min_y: (optional) minimum y coordinate of the canvas
        :param max_x: (optional) maximum x coordinate of the canvas
        :param max_y: (optional) maximum y coordinate of the canvas