docs: def by_user(self):  # pragma: no cover
          """
          Display group membership sorted by group.
  
          Returns:
              Array with a dictionary of group membership.
                  For example: {'test.user': ['testgroup', 'testgroup2']}
  
          """
          users = [i for i in self.__get_users()]
          user_groups = {}
          group_results = {
              tuple(value): key
              for (key, value) in self.by_group().items()
          }
          for user in users:
              user_groups[user] = []
              for user_list, group in group_results.items():
                  if user in user_list:
                      user_groups[user].append(group)
  
          return user_groups