code: def find_users_by_email_and_group(email_prefix=None, group=None, cursor=None, page_size=30):
      
      email_prefix = email_prefix or ''
  
      return ModelSearchCommand(MainUser.query_email_and_group(email_prefix, group),
                                page_size, cursor, cache_begin=None)
docs: Returns a command that retrieves users by its email_prefix, ordered by email and by Group.
      If Group is None, only users without any group are going to be searched
      It returns a max number of users defined by page_size arg. Next result can be retrieved using cursor, in
      a next call. It is provided in cursor attribute from command.