code: def _calc_map_expectation_success(self, success_count, nonnull_count, mostly):
          
  
          if nonnull_count > 0:
              # percent_success = float(success_count)/nonnull_count
              percent_success = success_count / nonnull_count
  
              if mostly != None:
                  success = bool(percent_success >= mostly)
  
              else:
                  success = bool(nonnull_count-success_count == 0)
  
          else:
              success = True
              percent_success = None
  
          return success, percent_success
docs: Calculate success and percent_success for column_map_expectations
  
          Args:
              success_count (int): \
                  The number of successful values in the column
              nonnull_count (int): \
                  The number of nonnull values in the column
              mostly (float or None): \
                  A value between 0 and 1 (or None), indicating the percentage of successes required to pass the expectation as a whole\
                  If mostly=None, then all values must succeed in order for the expectation as a whole to succeed.
  
          Returns:
              success (boolean), percent_success (float)