code: def find_in_registry(category = None, namespace = None, name = None):
      
      selected_registry = registry
      if category is not None:
          selected_registry = [re for re in selected_registry if re.category==category]
      if namespace is not None:
          selected_registry = [re for re in selected_registry if re.namespace==namespace]
      if name is not None:
          selected_registry = [re for re in selected_registry if re.name==name]
      if len(selected_registry)>0:
          return [sr.cls for sr in selected_registry]
  
      return None
docs: Find a given category/namespace/name combination in the registry
      category - string, see utils.inputs.registrycategories
      namespace - module namespace, see settings.NAMESPACE
      name - lowercase name of module