FlexForm from rpw.ui.forms

I am having trouble creating a basic script to test out using FlexForm from rpw.ui.forms to take multiple user inputs.
I get type error "takes exactly 3 arguments(2 given).

When i Copy the code from the documentation i get the same type of error, but it refers to the script in pyrevit library.

I also tried copying some code with flex form from pyChilizer from github, but get the same problem.

Can someone help me understand what it going wrong here?

And my code:

from rpw.ui.forms import FlexForm, Label, ComboBox, TextBox, Separator, Button, CheckBox

components = [Label("Choose View Template"),
              ComboBox("combobox2", {"Opt 1":10.00, "opt2":20.0}),
              TextBox("textbox1", Text="EIHD"),
              CheckBox("Use same prefix for all views"),
              Button("Create Views")]

form = FlexForm("ViewSet Creator", components)