code: @Inline(value="$3.$4addAll($1, $2)", imported=Iterables.class)
  	public static <E> boolean operator_add(Collection<E> collection, Iterable<? extends E> newElements) {
  		return addAll(collection, newElements);
  	}
docs: The operator mapping from {@code +=} to {@link #addAll(Collection, Iterable)}. Returns <code>true</code> if the
  collection changed due to this operation.
  
  @param collection
  the to-be-changed collection. May not be <code>null</code>.
  @param newElements
  elements to be inserted into the collection. May not be <code>null</code> but may contain
  <code>null</code> elements if the the target collection supports <code>null</code> elements.
  @return <code>true</code> if the collection changed due to this operation.
  @see #addAll(Collection, Iterable)