'Callback to handle the start of a hash
`key` is the redis key
`cardinality` is the number of elements in this set
`expiry` is a `datetime` object. None means the object does not expire
`info` is a dictionary containing additional information about this object.
After `start_set`, the  method `sadd` will be called with `key` exactly `cardinality` times
After that, the `end_set` method will be called to indicate the end of the set.
Note : This callback handles both Int Sets and Regular Sets'

def start_set(self, key, cardinality, expiry, info):

    pass
