Assign array to key dictionary in python

I'm not guru in python. I don't get why I can't assign an array of values to a key for this dictioary with this def.

This is how I use the sdk definition.

retu_keys_list = []
retu_keys_list.append('id')
retu_keys_list.append('transaction.amount')
redirect.retuKeys(retu_keys_list)

This is the specific definition in the sdk I use https://github.com/OptimalPayments/Python_SDK/blob/63e1ae662a4447bd65c907563eec9effc602dd74/src/PythonNetBanxSDK/HostedPayment/Redirect.py

'''
Property Retu Keys
'''   
def retuKeys(self, retu_keys):
    self.__dict__['retuKeys'] = retu_keys

From what I could debug, the problems comes when converting the array into json to be sent.The loop finds the array and try to convert the elements inside (strings), but since by default the loop consider each given parameter as array, the code throw an exception, and the retuKeys parameter is skipped...