def _assert_strides_are_log2_contiguous(strides):
    """
    Assert that each stride is 2x times its preceding stride, i.e. "contiguous in log2".
    """
    for i, stride in enumerate(strides[1:], 1):
        assert (
            stride == 2 * strides[i - 1]
        ), "Strides {} {} are not log2 contiguous".format(stride, strides[i - 1])
Assert that each stride is 2x times its preceding stride, i.e. "contiguous in log2".
examples/02_detectron2/modeling/backbone/fpn.py