docs: def regenerate_prefixes(self, *args):
          """Regenerate the cache of command prefixes based on nick etc."""
          nick = self.controller.client.user.nick
          self.prefixes = set([
              nick + ": ",
              nick + ", ",
              nick + " - ",
          ])
          # Include lower-case versions as well, but not caps
          self.prefixes.update([p.lower() for p in self.prefixes])
          if self.sigil:
              self.prefixes.add(self.sigil)