class Test:
    def __getitem__(self, arg):
        print(arg)


test = Test()
 
test[1]      # 1
test[1:]     # slice(1, None, None)
test[1:3]    # slice(1, 3, None)
test[1:3:2]  # slice(1, 3, 2)

test['abc']     # abc

test[...]       # Ellipsis
test[:, ...]    # (slice(None, None, None), Ellipsis)
test[::3, ...]  # (slice(None, None, 3), Ellipsis)

test[:, :, :]   # (slice(None, None, None), slice(None, None, None), slice(None, None, None))
test[...]       # Ellipsis

test[1, 2, 3]   # (1, 2, 3)