def content(self, trim_left, trim_top, cols, rows, attr):
        def_attr = None
        if attr and None in attr:
            def_attr = attr[None]
        line = [(def_attr, None, bytes().rjust(cols))]
        for i in range(rows):
            yield line
return (cols, rows) of spaces with default attributes.
dataset/ETHPy150Open AnyMesh/anyMesh-Python/example/urwid/canvas.py/BlankCanvas.content