public ValueUpdate setValueUpdate(int index, ValueUpdate update) {
        return valueUpdates.set(index, update);
    }
Replaces the value update at the specified position in the list of value updates
with the specified value update.

@param index index of value update to replace
@param update value update to be stored at the specified position
@return the value update previously at the specified position
@throws IndexOutOfBoundsException if index out of range (index &lt; 0 || index &gt;= size())
document/src/main/java/com/yahoo/document/update/FieldUpdate.java