docs: def update_attribute_value_items(self):
          """
          Returns an iterator of items for an attribute value map to use for
          an UPDATE operation.
  
          The iterator ignores collection attributes as these are processed
          implicitly by the traversal algorithm.
  
          :returns: iterator yielding tuples with objects implementing
            :class:`everest.resources.interfaces.IResourceAttribute` as the
            first and the proxied attribute value as the second argument.
          """
          for attr in self._attribute_iterator():
              if attr.kind != RESOURCE_ATTRIBUTE_KINDS.COLLECTION:
                  try:
                      attr_val = self._get_proxied_attribute_value(attr)
                  except AttributeError:
                      continue
                  else:
                      yield (attr, attr_val)