def METHOD_NAME():
    np.testing.assert_equal(cirq.KET_ZERO.projector(), [[1, 0], [0, 0]])
    np.testing.assert_equal(cirq.KET_ONE.projector(), [[0, 0], [0, 1]])
    np.testing.assert_allclose(cirq.KET_PLUS.projector(), np.array([[1, 1], [1, 1]]) / 2)
    np.testing.assert_allclose(cirq.KET_MINUS.projector(), np.array([[1, -1], [-1, 1]]) / 2)