code: def rho_hv(scatterer):
      
      Z = scatterer.get_Z()
      a = (Z[2,2] + Z[3,3])**2 + (Z[3,2] - Z[2,3])**2
      b = (Z[0,0] - Z[0,1] - Z[1,0] + Z[1,1])
      c = (Z[0,0] + Z[0,1] + Z[1,0] + Z[1,1])
      return np.sqrt(a / (b*c))
docs: Copolarized correlation (rho_hv) for the current setup.
  
      Args:
          scatterer: a Scatterer instance.
  
      Returns:
         rho_hv.