code: def is_filled(self, point):
          
          index = self.point_to_index(point)
          in_range = (np.array(index) < np.array(self.shape)).all()
          if in_range:
              is_filled = self.matrix[index]
          else:
              is_filled = False
          return is_filled
docs: Query a point to see if the voxel cell it lies in is filled or not.
  
          Parameters
          ----------
          point: (3,) float, point in space
  
          Returns
          ---------
          is_filled: bool, is cell occupied or not