function validateExplicitKey(element, parentType) {
  if (!element._store || element._store.validated || element.key != null) {
    return;
  }
  element._store.validated = true;

  var addenda = getAddendaForKeyUse('uniqueKey', element, parentType);
  if (addenda === null) {
    // we already showed the warning
    return;
  }
  "development" !== 'production' ? warning(false, 'Each child in an array or iterator should have a unique "key" prop.' + '%s%s%s', addenda.parentOrOwner || '', addenda.childOwner || '', addenda.url || '') : undefined;
}
Warn if the element doesn't have an explicit key assigned to it.
This element is in an array. The array could grow and shrink or be
reordered. All children that haven't already been validated are required to
have a "key" property assigned to it.

@internal
@param {ReactElement} element Element that requires a key.
@param {*} parentType element's parent's type.