If there are multiple values for a key, CQL grammar choses last value. This should not be silent or should not be allowed.

If through CQL, multiple values are specified for a key, grammar parses the map and last value for the key wins. This behavior is bad.
e.g.

CREATE KEYSPACE Excalibur WITH REPLICATION = {'class': 'NetworkTopologyStrategy', 'dc1': 2, 'dc1': 5};

Parsing this statement, 'dc1' gets RF = 5. This can be catastrophic, may even result in loss of data. This behavior should not be silent or not be allowed at all.