def create_withdrawal(self, asset, amount, private_key):
        """
        Function to create a withdrawal request by generating a withdrawal ID request from the Switcheo API.
        Execution of this function is as follows::

            create_withdrawal(asset="SWTH", amount=1.1, private_key=kp)

        The expected return result for this function is as follows::

            {
                'id': 'a5a4d396-fa9f-4191-bf50-39a3d06d5e0d'
            }

        :param asset:  Script Hash of asset ID from the available products.
        :type asset: str
        :param amount: The amount of coins/tokens to be withdrawn.
        :type amount: float
        :param private_key: The Private Key (ETH) or KeyPair (NEO) for the wallet being used to sign deposit message.
        :type private_key: KeyPair or str
        :return: Dictionary with the withdrawal ID generated by the Switcheo API.
        """
        signable_params = {
            'blockchain': self.blockchain,
            'asset_id': asset,
            'amount': str(self.blockchain_amount[self.blockchain](amount)),
            'timestamp': get_epoch_milliseconds(),
            'contract_hash': self.contract_hash
        }
        api_params = self.sign_create_withdrawal_function[self.blockchain](signable_params, private_key)
        return self.request.post(path='/withdrawals', json_data=api_params)
Function to create a withdrawal request by generating a withdrawal ID request from the Switcheo API.
        Execution of this function is as follows::

            create_withdrawal(asset="SWTH", amount=1.1, private_key=kp)

        The expected return result for this function is as follows::

            {
                'id': 'a5a4d396-fa9f-4191-bf50-39a3d06d5e0d'
            }

        :param asset:  Script Hash of asset ID from the available products.
        :type asset: str
        :param amount: The amount of coins/tokens to be withdrawn.
        :type amount: float
        :param private_key: The Private Key (ETH) or KeyPair (NEO) for the wallet being used to sign deposit message.
        :type private_key: KeyPair or str
        :return: Dictionary with the withdrawal ID generated by the Switcheo API.