code: def sharp(self) -> 'Channel':
          r
  
          N = self.qubit_nb
  
          tensor = self.tensor
          tensor = bk.reshape(tensor, [2**N] * 4)
          tensor = bk.transpose(tensor, (0, 2, 1, 3))
          tensor = bk.reshape(tensor, [2] * 4 * N)
          return Channel(tensor, self.qubits)
docs: r"""Return the 'sharp' transpose of the superoperator.
  
          The transpose :math:`S^\#` switches the two covariant (bra)
          indices of the superoperator. (Which in our representation
          are the 2nd and 3rd super-indices)
  
          If :math:`S^\#` is Hermitian, then :math:`S` is a Hermitian-map
          (i.e. transforms Hermitian operators to hJrmitian operators)
  
          Flattening the :math:`S^\#` superoperator to a matrix gives
          the Choi matrix representation. (See channel.choi())