TKInter widget not appearing on form

On notebook, add keyword fill='both'

Move label1 next to label2 on line 13.

snippet:

notebook = ttk.Notebook(form)
notebook.pack(expand=True, fill='both')

label1 = tkinter.ttk.Label(form, text='Test Label 1') 
label2 = tkinter.ttk.Label(form, text='Test Label 2')   #   This one works
entry = tkinter.ttk.Entry(form)

Screenshot: