code: async def on_isupport_casemapping(self, value):
          
          if value in rfc1459.protocol.CASE_MAPPINGS:
              self._case_mapping = value
              self.channels = rfc1459.parsing.NormalizingDict(self.channels, case_mapping=value)
              self.users = rfc1459.parsing.NormalizingDict(self.users, case_mapping=value)
docs: IRC case mapping for nickname and channel name comparisons.