docs: def downsampled_mesh(self, step):
          """Returns a downsampled copy of this mesh.
  
          Args:
              step: the step size for the sampling
  
          Returns:
              a new, downsampled Mesh object.
  
          Raises:
              ValueError if this Mesh has faces.
          """
          from lace.mesh import Mesh
  
          if self.f is not None:
              raise ValueError(
                  'Function `downsampled_mesh` does not support faces.')
  
          low = Mesh()
          if self.v is not None:
              low.v = self.v[::step]
          if self.vc is not None:
              low.vc = self.vc[::step]
          return low