code: def remove_cycle_mrkr(self):
          
          window_start = self.parent.value('window_start')
  
          try:
              self.annot.remove_cycle_mrkr(window_start)
  
          except KeyError:
              msg = ('The start of the window does not correspond to any cycle '
                     'marker in sleep scoring file')
              self.parent.statusBar().showMessage(msg)
              lg.debug(msg)
  
          else:
              lg.debug('User removed cycle marker at' + str(window_start))
              #self.trace
              self.parent.overview.update(reset=False)
              self.parent.overview.display_annotations()
docs: Remove cycle marker.