dump.py

    def sign_data(self, data=None):                                                                   
        signature = hmac.new(self._token, msg=bytes(self._user, 'utf8'), digestmod=hashlib.sha512)    
        if data:                                                                                      
            signature.update(bytes(json.dumps(data, sort_keys=True, indent=4, separators=(',', ': ')),'utf8'))
        signed_data = {'user' : self._user, 'signature' : signature.hexdigest()}                      
        if data != None:                                                                              
            signed_data['data'] = data                                                                
                                                                                                      
        return signed_data