Interface representing a filter node.
| filterId | The filter identifier. |
| filterValue | The filter value. This can be null or empty if the value has not been written yet. |
| operatorId | The operator identifier. This can be null or empty if the operator has not been written yet. |
| paramValue | The parameter value. This can be null or empty if the filter is not a filter function, or there is no parameter written yet. |