class_docstr: Class for controlling display and output settings.
class_docstr_tok: ["Class","for","controlling","display","and","output","settings","."]
code: def missing_backend_exception(value, keyword, allowed):
      if value in OutputSettings.backend_list:
          raise ValueError(
              f"Backend {value!r} not available. Has it been loaded with the notebook_extension?"
          )
      else:
          raise ValueError(f"Backend {value!r} does not exist")
  
imports: from collections import defaultdict
  from ..core import Store
label_desc: Use image node_id 2 for calling the OutputSettings obj's underlying member method code with example usage: obj.missing_backend_exception(value, keyword, allowed) without return types