Returns a Boolean stating whether the object is in the container.
A [not] in B
- A
- Any valid object.
- B
- Any valid object.
#TODO
O(1) for dict O(1) to O(n) for sets O(n) for sequences (str, list, tuple)
When used with dictionaries checks the keys instead of values.
>>> 'A' in 'ABCD'
True
>>> 0 in [0, 1, 2]
True
>>> 0 not in {'a': 0, 'b': 1}
True#TODO