Overlapping 'format' attribute in shopify_python_api by varesa

I have spent my day trying to create a CarrierService using the shopify_python_api (https://github.com/Shopify/shopify_python_api).

I tried replicating the example POST request from the API docs:
 

Create a carrier service

POST /admin/carrier_services.json

{
  "carrier_service": {"name": "Shipping Rate Provider","callback_url": "http://shippingrateprovider.com","format": "json","service_discovery": true
  }
}

A short snippet:

import shopify as s

c = s.CarrierService()
c.name = "Shipping rate provider"
c.callback_url = "http://shippingrateprovider.com/callback"
c.format = "json"
c.service_discovery = "false"
c.save()

After getting tired of seeing "422 Unprocessible Entity" I added a few print()s to pyactiveresource, which shows my request:

POST: /admin/carrier_services.json
b'{"carrier_service": {"name": "Shipping rate provider", "callback_url": "http://shippingrateprovider.com/callback", "service_discovery": "false"}
}'

It turns out that `format` goes missing.

It would seem to come down to these lines pyactiveresource.py:

    def __setattr__(self, name, value):"""Set the named attributes.

        Args:
            name: The attribute name.
            value: The attribute's value.
        Returns:
            None"""
        if '_initialized' in self.__dict__:
            if name in self.__dict__ or getattr(self.__class__, name, None):
                # Update a normal attribute
                object.__setattr__(self, name, value)
            else:
                # Add/update an attribute
                self.attributes[name] = value<rest cut out>

I assume that the way it was inteded to work is it to go to the else-block:

self.attributes['format'] = 'json'

But because 'format' is a field in the pyactiveresource object (defines what format it e.g. POSTs in), the 'json' instead goes to

# Update a normal attribute
object.__setattr__(self, name, value)

The resulting JSON is generated from 'self.attributes'

Has anyone else encountered this problem or am I doing something wrong?