code: def rhombohedral(a: float, alpha: float):
          
          return Lattice.from_parameters(a, a, a, alpha, alpha, alpha)
docs: Convenience constructor for a rhombohedral lattice.
  
          Args:
              a (float): *a* lattice parameter of the rhombohedral cell.
              alpha (float): Angle for the rhombohedral lattice in degrees.
  
          Returns:
              Rhombohedral lattice of dimensions a x a x a.