docs: def cdot(L, out=None):
      r"""Product of a Cholesky matrix with itself transposed.
  
      Args:
          L (array_like): Cholesky matrix.
          out (:class:`numpy.ndarray`, optional): copy result to.
  
      Returns:
          :class:`numpy.ndarray`: :math:`\mathrm L\mathrm L^\intercal`.
      """
      L = asarray(L, float)
  
      layout_error = "Wrong matrix layout."
  
      if L.ndim != 2:
          raise ValueError(layout_error)
  
      if L.shape[0] != L.shape[1]:
          raise ValueError(layout_error)
  
      if out is None:
          out = empty((L.shape[0], L.shape[1]), float)
  
      return einsum("ij,kj->ik", L, L, out=out)