code: def __has_no_dependents (self, obj, constraints):
          
          failed = False
          while constraints and not failed:
              c = constraints [0]
  
              if c [1] == obj:
                  failed = True
  
              constraints = constraints [1:]
  
          return not failed
docs: Returns true if there's no constraint in 'constraints' where
              'obj' comes second.