docs: public static SingleInputSemanticProperties addSourceFieldOffset(SingleInputSemanticProperties props,
  																		int numInputFields, int offset) {
  
  		SingleInputSemanticProperties offsetProps = new SingleInputSemanticProperties();
  		if (props.getReadFields(0) != null) {
  			FieldSet offsetReadFields = new FieldSet();
  			for (int r : props.getReadFields(0)) {
  				offsetReadFields = offsetReadFields.addField(r + offset);
  			}
  			offsetProps.addReadFields(offsetReadFields);
  		}
  		for (int s = 0; s < numInputFields; s++) {
  			FieldSet targetFields = props.getForwardingTargetFields(0, s);
  			for (int t : targetFields) {
  				offsetProps.addForwardedField(s + offset, t);
  			}
  		}
  		return offsetProps;
  	}