Panda3D Collision Detection: How to Fix 'NameError: name 'CollisionSphere' is not defined'

It seems that the code is missing an import statement for CollisionSphere from the panda3d.core module. Adding the following line at the top of the file should fix the error:

from panda3d.core import CollisionTraverser, CollisionNode, CollisionHandlerQueue, CollisionRay, CollisionSphere

This line imports the CollisionSphere class, which is required for creating collision solids in Panda3D. Once you add this line, the code should run without any errors.