code: def add(self, resource):
          
          if isinstance(resource, collections.Iterable):
              for r in resource:
                  self.add_if_changed(r)
          else:
              self.add_if_changed(resource)
docs: Add a resource change or an iterable collection of them.
  
          Allows multiple resource_change objects for the same
          resource (ie. URI) and preserves the order of addition.