code: def case(self, case_id=None):
          
          if case_id:
              for case in self.case_objs:
                  if case.case_id == case_id:
                      return case
          else:
              if self.cases:
                  return list(self.case_objs)[0]
  
          return Case(case_id='unknown')
docs: Return a Case object
  
              If no case_id is given return one case
  
              Args:
                  case_id (str): A case id
  
              Returns:
                  A Case object