Determine / Set ActivityContext in Invoke Code

I am trying to get an activity, ReadPDFText, to fire inside of an Invoke Code activity instead of in a regular UiPath activity through the low code. My reasoning is that I need my workflow to be faster and more performant, and the low code iterators are significantly slower at runtime than iterators inside of Invoke Code.

So to fire the activity properly, it looks like I need to set the ReadPDFText.Text to an output string.
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But the first arg of that ‘Set’ method is an ‘ActivityContext’ for which I have no documentation and no useful help from the intellisense on how to create.

May I please have some help on how to complete this block with something more functional than ‘null’? Thanks

		string sPageText = "";
		ReadPDFText PageText = new UiPath.PDF.Activities.ReadPDFText();
		PageText.FileName = in_TransactionItem;
		PageText.Range = String.Format("{0}-{0}", i);
		PageText.Text.Set(null, sPageText);
		WorkflowInvoker wfi = new WorkflowInvoker(PageText);
		wfi.Invoke();