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