@Override
	public String toString() {
		return super.toString() + ", OpRep = " + rep + ", subOpIndex = " + subOpIndex +
			", VariableOffset = " + variableOffset;
	}
Returns the sub operand index at this location.
<p>
This index can be used on the instruction.getOpObjects() to find the actual object (Address,
Register, Scalar) the cursor is over.
@return 0-n if over a valid OpObject, -1 otherwise
Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/util/OperandFieldLocation.java