class_docstr: Registers fake backends with the Store to test options on.
class_docstr_tok: ["Registers","fake","backends","with","the","Store","to","test","options","on","."]
code: def register_custom(
      cls, objtype, backend, custom_plot=None, custom_style=None
  ):
      if custom_style is None:
          custom_style = []
      if custom_plot is None:
          custom_plot = []
      groups = Options._option_groups
      if backend not in Store._options:
          Store._options[backend] = OptionTree([], groups=groups)
          Store._custom_options[backend] = {}
      name = objtype.__name__
      style_opts = Keywords(
          ["style_opt1", "style_opt2"] + custom_style, name
      )
      plot_opts = Keywords(
          ["plot_opt1", "plot_opt2"] + custom_plot, name
      )
      opt_groups = {
          "plot": Options(allowed_keywords=plot_opts),
          "style": Options(allowed_keywords=style_opts),
          "output": Options(allowed_keywords=["backend"]),
      }
      Store._options[backend][name] = opt_groups
      Store.renderers[backend] = MockRenderer(backend)
  
imports: import gc
  from holoviews.core.element import Element
  from holoviews.core.options import Keywords, Options, OptionTree, Store
  from holoviews.core.spaces import HoloMap
  from ..utils import LoggingComparisonTestCase
label_desc: Use image node_id 3 for calling the CustomBackendTestCase obj's underlying member method code with example usage: obj.register_custom(cls, objtype, backend, custom_plot, custom_style) without return types