old_contents: from .camera import Camera
  from .scene import Scene, Element, Light
  from .version import __version__
  from .grid import Grid
  from .homogeneous import (translate, scale, rotatex, rotatey, rotatez, rotatexyz,
                            rotate_axis, cross)
  from .geometry import Geometry, BBox
  
new_contents: '''
  Volpy
  =====
  
  A fast volume rendering implementation for Python. Volpy has support for:
  
    1. Multithreading or multiprocessing at the rendering step
    2. Native implementation of ray casting
    3. Native access to NumPy arrays during rendering
    4. Support for ambient and diffuse lighting terms
  
  How to use this package
  -----------------------
  
  Volpy is organized into several different modules but the API is imported into
  the root of the package. Therefore, you should write your code like this:
  
      >>> import volpy
      >>> scene = volpy.Scene(ambient=my_func)
  
  '''
  from .camera import Camera
  from .scene import Scene, Element, Light
  from .version import __version__
  from .grid import Grid
  from .homogeneous import (translate, scale, rotatex, rotatey, rotatez, rotatexyz,
                            rotate_axis, cross)
  from .geometry import Geometry, BBox
  
subject: Write a docstring for the package