code: def collision(self):
          
          i = self._collision
          for name, _i in COLLISIONS.items():
              if i==_i:
                  return name
          return i
docs: Get or set the collision module.
  
          Available collision modules are:
  
          - ``'none'`` (default)
          - ``'direct'``
          - ``'tree'``
          - ``'mercurius'`` 
          - ``'direct'``
          
          Check the online documentation for a full description of each of the modules.