public static FieldUpdate create(Field field) {
        return new FieldUpdate(field);
    }
Creates a new, empty field update with no encapsulated value updates. Use this method to add an arbitrary
set of value updates using the FieldUpdate.addValueUpdate() method.

@param field the Field to alter
@return a new, empty FieldUpdate
@see com.yahoo.document.update.ValueUpdate
@see FieldUpdate#addValueUpdate(ValueUpdate)
document/src/main/java/com/yahoo/document/update/FieldUpdate.java