async def signmessage(self, address, message, password=None, wallet: Abstract_Wallet = None):
        """Sign a message with a key. Use quotes if your message contains
        whitespaces

        arg:str:address:Bitcoin address
        arg:str:message:Clear text message. Use quotes if it contains spaces.
        """
        sig = wallet.sign_message(address, message, password)
        return base64.b64encode(sig).decode('ascii')
Sign a message with a key. Use quotes if your message contains
        whitespaces

        arg:str:address:Bitcoin address
        arg:str:message:Clear text message. Use quotes if it contains spaces.
        
electrum/commands.py