def test__key():
"""Test Attribute hash key."""
A = Attribute("", [])
A2 = Attribute("label", [1, 'string', True])
assert A._key() == ("", 'V()')
print A2._key()
assert A2._key() == ('label', 'V(1, string, True)')
def test___hash__():
"""test hash function for Attribute."""
A = Attribute("label", [1, "string", True])
B = Attribute("", [])
assert type(hash(B._key())) == int
assert type(hash(A._key())) == int
