Extending existing panels?

Blender already has a panel which seems like the logical place for the UI I wish to add. So is there a way to extend an existing panel from a addon (don’t want to edit the files directly) rather than having to add a new one?

Worked it out in the end:

from bpy import types

def example(self, context):
    self.layout.label(text="Example")

types.DATA_PT_camera_display.append(example)