Problem with CreateCorePluginConfiguration

I'm trying to start automating the process of node autodiscovery.  Looks like the 1st part is to generate a config with CreateCorePluginConfiguration.  When invoke this, I get the following error message:

{'Message': 'Verb Orion.Discovery.CreateCorePluginConfiguration cannot unpackage parameter 0'}

This is my python code:

def main():

    swis = SwisClient('localhost', 'admin', '')

    config = swis.invoke('Orion.Discovery', 'CreateCorePluginConfiguration',

    {

      'BulkList': [{'Address':'10.199.10.12'}],

      #'IpRanges': [], # Optional

      #'Subnets': None, # Optional

      'Credentials': [

        {'CredentialID':1, 'Order':1},

        {'CredentialID':2, 'Order':2},

      ],

      'WmiRetriesCount': 1,

      'WmiRetryIntervalMiliseconds': 1000

    })

I'm running the following:

Orion 2013.2.0, NPM 10.6

Thanks,

Larry