function getAddendaForKeyUse(messageType, element, parentType) {
  var addendum = getDeclarationErrorAddendum();
  if (!addendum) {
    var parentName = typeof parentType === 'string' ? parentType : parentType.displayName || parentType.name;
    if (parentName) {
      addendum = ' Check the top-level render call using <' + parentName + '>.';
    }
  }

  var memoizer = ownerHasKeyUseWarning[messageType] || (ownerHasKeyUseWarning[messageType] = {});
  if (memoizer[addendum]) {
    return null;
  }
  memoizer[addendum] = true;

  var addenda = {
    parentOrOwner: addendum,
    url: ' See https://fb.me/react-warning-keys for more information.',
    childOwner: null
  };

  // Usually the current owner is the offender, but if it accepts children as a
  // property, it may be the creator of the child that's responsible for
  // assigning it a key.
  if (element && element._owner && element._owner !== ReactCurrentOwner.current) {
    // Give the component that originally created this child.
    addenda.childOwner = ' It was passed a child from ' + element._owner.getName() + '.';
  }

  return addenda;
}
Shared warning and monitoring code for the key warnings.

@internal
@param {string} messageType A key used for de-duping warnings.
@param {ReactElement} element Component that requires a key.
@param {*} parentType element's parent's type.
@returns {?object} A set of addenda to use in the warning message, or null
if the warning has already been shown before (and shouldn't be shown again).