docs: def is_active(self, key, *instances, **kwargs):
          """
          Returns ``True`` if any of ``instances`` match an active switch.
          Otherwise returns ``False``.
  
          >>> operator.is_active('my_feature', request) #doctest: +SKIP
          """
          try:
              default = kwargs.pop('default', False)
  
              # Check all parents for a disabled state
              parts = key.split(':')
              if len(parts) > 1:
                  child_kwargs = kwargs.copy()
                  child_kwargs['default'] = None
                  result = self.is_active(':'.join(parts[:-1]), *instances,
                                          **child_kwargs)
  
                  if result is False:
                      return result
                  elif result is True:
                      default = result
  
              try:
                  switch = self[key]
              except KeyError:
                  # switch is not defined, defer to parent
                  return default
  
              if switch.status == GLOBAL:
                  return True
              elif switch.status == DISABLED:
                  return False
              elif switch.status == INHERIT:
                  return default
  
              conditions = switch.value
              # If no conditions are set, we inherit from parents
              if not conditions:
                  return default
  
              instances = list(instances) if instances else []
              instances.extend(self.context.values())
  
              # check each switch to see if it can execute
              return_value = False
  
              for namespace, condition in conditions.iteritems():
                  condition_set = registry_by_namespace.get(namespace)
                  if not condition_set:
                      continue
                  result = condition_set.has_active_condition(condition,
                                                              instances)
                  if result is False:
                      return False
                  elif result is True:
                      return_value = True
          except:
              log.exception('Error checking if switch "%s" is active', key)
              return_value = False
  
          # there were no matching conditions, so it must not be enabled
          return return_value