>>> my = distinctdict()
>>> my['key'] = 'value'
>>> my['other_key'] = 'value'
Traceback (most recent call last):
File "<input>", line 1, in <module>
File "<input>", line 10, in __setitem__
DistinctError: This value already exists for different key
>>> my['other_key'] = 'value2'
>>> my
{'key': 'value', 'other_key': 'value2'