code: def crypto_withdraw(self, amount, currency, crypto_address):
          
          params = {'amount': amount,
                    'currency': currency,
                    'crypto_address': crypto_address}
          return self._send_message('post', '/withdrawals/crypto',
                                    data=json.dumps(params))
docs: Withdraw funds to a crypto address.
  
          Args:
              amount (Decimal): The amount to withdraw
              currency (str): The type of currency (eg. 'BTC')
              crypto_address (str): Crypto address to withdraw to.
  
          Returns:
              dict: Withdraw details. Example::
                  {
                      "id":"593533d2-ff31-46e0-b22e-ca754147a96a",
                      "amount":"10.00",
                      "currency": "BTC",
                  }