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