def METHOD_NAME(tmp_path):
    # "/a" and "a" are the same for LocalFileSystem
    tmp_path.joinpath("a").write_bytes(b"data")
    m = fsspec.get_mapper(f"file://{tmp_path}")
    assert m["/a"] == m["a"] == b"data"
    # "/a" and "a" differ for MemoryFileSystem
    m = fsspec.get_mapper(f"memory://{uuid.uuid4()}")
    m["/a"] = b"data"
    assert m["/a"] == b"data"
    with pytest.raises(KeyError):
        _ = m["a"]