code: @Nullable
  	private static XField getFieldFromStack(final OpcodeStack stk, final String signature) {
  		int parmCount = SignatureUtils.getNumParameters(signature);
  		if (stk.getStackDepth() > parmCount) {
  			OpcodeStack.Item itm = stk.getStackItem(parmCount);
  			return itm.getXField();
  		}
  		return null;
  	}
docs: return the field object that the current method was called on, by finding the
  reference down in the stack based on the number of parameters
  
  @param stk       the opcode stack where fields are stored
  @param signature the signature of the called method
  
  @return the field annotation for the field whose method was executed