docs: def fill_missing(self):
          """
          We do not want TLSServerKeyExchange.build() to overload and recompute
          things every time it is called. This method can be called specifically
          to have things filled in a smart fashion.
  
          Note that we do not expect default_params.g to be more than 0xff.
          """
          s = self.tls_session
  
          default_params = _ffdh_groups['modp2048'][0].parameter_numbers()
          default_mLen = _ffdh_groups['modp2048'][1]
  
          if not self.dh_p:
              self.dh_p = pkcs_i2osp(default_params.p, default_mLen // 8)
          if self.dh_plen is None:
              self.dh_plen = len(self.dh_p)
  
          if not self.dh_g:
              self.dh_g = pkcs_i2osp(default_params.g, 1)
          if self.dh_glen is None:
              self.dh_glen = 1
  
          p = pkcs_os2ip(self.dh_p)
          g = pkcs_os2ip(self.dh_g)
          real_params = dh.DHParameterNumbers(p, g).parameters(default_backend())
  
          if not self.dh_Ys:
              s.server_kx_privkey = real_params.generate_private_key()
              pubkey = s.server_kx_privkey.public_key()
              y = pubkey.public_numbers().y
              self.dh_Ys = pkcs_i2osp(y, pubkey.key_size // 8)
          # else, we assume that the user wrote the server_kx_privkey by himself
          if self.dh_Yslen is None:
              self.dh_Yslen = len(self.dh_Ys)
  
          if not s.client_kx_ffdh_params:
              s.client_kx_ffdh_params = real_params