docs: def set_mime_type(self, mime_type):
          """
          Update the highlighter lexer based on a mime type.
  
          :param mime_type: mime type of the new lexer to setup.
          """
          try:
              self.set_lexer_from_mime_type(mime_type)
          except ClassNotFound:
              _logger().exception('failed to get lexer from mimetype')
              self._lexer = TextLexer()
              return False
          except ImportError:
              # import error while loading some pygments plugins, the editor
              # should not crash
              _logger().warning('failed to get lexer from mimetype (%s)' %
                                mime_type)
              self._lexer = TextLexer()
              return False
          else:
              return True