code: def qteSetLexer(self, lexer):
          if (lexer is not None) and (not issubclass(lexer, Qsci.QsciLexer)):
              QtmacsOtherError('lexer must be a class object and derived from'
                               ' <b>QsciLexer</b>')
              return
          self.qteLastLexer = lexer
          if lexer is None:
              self.setLexer(None)
          else:
              self.setLexer(lexer())
          self.setMonospace()