docs: def unregister_plotter(identifier, sorter=True, plot_func=True):
      """
      Unregister a :class:`psyplot.plotter.Plotter` for the projects
  
      Parameters
      ----------
      identifier: str
          Name of the attribute that is used to filter for the instances
          belonging to this plotter or to create plots with this plotter
      sorter: bool
          If True, the identifier will be unregistered from the :class:`Project`
          class
      plot_func: bool
          If True, the identifier will be unregistered from the
          :class:`ProjectPlotter` class
      """
      d = registered_plotters.get(identifier, {})
      if sorter and hasattr(Project, identifier):
          delattr(Project, identifier)
          d['sorter'] = False
      if plot_func and hasattr(ProjectPlotter, identifier):
          for cls in [ProjectPlotter, DatasetPlotter, DataArrayPlotter]:
              delattr(cls, identifier)
          try:
              delattr(plot, '_' + identifier)
          except AttributeError:
              pass
          d['plot_func'] = False
      if sorter and plot_func:
          registered_plotters.pop(identifier, None)