code: def key_expand(self, key):
          
  
          key = self._process_value(key, 'privatekey')
  
          payload = {"key": key}
  
          resp = self.call('key_expand', payload)
  
          return resp
docs: Derive public key and account number from **private key**
  
          :param key: Private key to generate account and public key of
          :type key: str
  
          :raises: :py:exc:`nano.rpc.RPCException`
  
          >>> rpc.key_expand(
              key="781186FB9EF17DB6E3D1056550D9FAE5D5BBADA6A6BC370E4CBB938B1DC71DA3"
          )
          {
            "private": "781186FB9EF17DB6E3D1056550D9FAE5D5BBADA6A6BC370E4CBB938B1DC71DA3",
            "public": "3068BB1CA04525BB0E416C485FE6A67FD52540227D267CC8B6E8DA958A7FA039",
            "account": "xrb_1e5aqegc1jb7qe964u4adzmcezyo6o146zb8hm6dft8tkp79za3sxwjym5rx"
          }