It seems that the method .default_numbers_to_display() has been removed from Manim Community, but the code wasn't updated accordingly.
If your goal is to display numbers along the number line, you can do either of the following:

1. Use .add_numbers() after creating NumberLine object:

   class IntroductionToComplexNumbers(Scene):
       def construct(self):
           real_number_line = NumberLine(
               x_range=[-5, 5, 1],
               length=10,
               include_tip=False,
           )
           real_number_line.add_numbers()
           self.add(real_number_line)

2. Or, set include_numbers=True directly in the constructor:

   class IntroductionToComplexNumbers(Scene):
       def construct(self):
           real_number_line = NumberLine(
               x_range=[-5, 5, 1],
               length=10,
               include_tip=False,
               include_numbers=True,
           )
           self.add(real_number_line)

For more details, see the documentation:
👉 NumberLine — Manim Documentation

Hi @kevinnadar22

I think this issue still needs to be addressed.

When users call .get_number_mobjects() or .get_labels() on a NumberLine object, it will still raise an AttributeError because .default_numbers_to_display() is being accessed but doesn't exist.