code: def tetragonal(a: float, c: float):
          
          return Lattice.from_parameters(a, a, c, 90, 90, 90)
docs: Convenience constructor for a tetragonal lattice.
  
          Args:
              a (float): *a* lattice parameter of the tetragonal cell.
              c (float): *c* lattice parameter of the tetragonal cell.
  
          Returns:
              Tetragonal lattice of dimensions a x a x c.