code: def get_group_by_group_id(self, group_id):
          
          group_id_base64 = base64.b64encode(group_id).decode('ascii')
          groups = self.m["groups"]
          for g in groups:
              if (g["group_id"] == group_id_base64):
                  return g
          return None
docs: return group with given group_id (return None if doesn't exists)