code: public Object evaluateFunction(String functionName, Object[] arguments) throws Exception {
  		return evaluateFunction(functionName, null, arguments);
  	}
docs: Evaluates a function defined in ink.
  
  @param functionName
  The name of the function as declared in ink.
  @param arguments
  The arguments that the ink function takes, if any. Note that we
  don't (can't) do any validation on the number of arguments right
  now, so make sure you get it right!
  @return The return value as returned from the ink function with `~ return
  myValue`, or null if nothing is returned.
  @throws Exception