private Object getRowValueKey(final T rowValue) {
        return (keyProvider == null || rowValue == null)
                ? rowValue
                : keyProvider.getKey(rowValue);
    }
Get the key for the specified row value.

@param rowValue the row value
@return the key
stroom-core-client-widget/src/main/java/com/google/gwt/user/cellview/client/HasDataPresenter.java