code: def reduce_breakpoints(plugin, field_name, request=None, obj=None):
      
      if not isinstance(plugin, CascadePluginBase):
          raise ValueError('Plugin is not of type CascadePluginBase')
      parent_instance = plugin.get_parent_instance(request, obj)
      if not parent_instance:
          return
      complete_glossary = parent_instance.get_complete_glossary()
      if 'breakpoints' not in complete_glossary:
          return
      try:
          # find the glossary_field named field_name and restrict its breakpoint to the available ones
          widget = [f for f in plugin.glossary_fields if f.name == field_name][0].widget
      except IndexError:
          return
      if not isinstance(widget, widgets.MultiWidget):
          raise ValueError('Widget for glossary_field {0} is not a multiple value field')
      temp = [(l, widget.widgets[k]) for k, l in enumerate(widget.labels) if l in complete_glossary['breakpoints']]
      widget.labels, widget.widgets = (list(t) for t in zip(*temp))
docs: Narrow down the number of breakpoints in the widget of the named glossary_field. This is useful
      in case the container was defined with a subset of these breakpoints: xs, sm, md, lg.