def test_symbol():
    s = Symbol('s')
    assert (s.matches(s) == {})
    assert (s.matches(2) == None)
    assert (s.matches((2 + s)) == None)
    assert (s.matches((2 * s)) == None)
    assert (s.matches((s ** 2)) == None)
def test_symbol():
    s = Symbol('s')
    assert (s.matches(s) == {})
    assert (s.matches(2) == None)
    assert (s.matches((2 + s)) == None)
    assert (s.matches((2 * s)) == None)
    assert (s.matches((s ** 2)) == None)