graphene relation using RESTfull API as data source

I'm using django graphene for building a graphql server, it consume a RESTfull API to get data, following this schema:

class DeviceType(graphene.ObjectType):
    id = graphene.ID()
    reference = graphene.String()
    serial = graphene.Float()

class InstallationType(graphene.ObjectType):
    id = graphene.ID()
    company = graphene.Int()
    device = graphene.ID()

class AllDataType(graphene.ObjectType):
    device = graphene.Field(DeviceType)
    installation = graphene.Field(InstallationType)

class Query(graphene.ObjectType):
    installation = graphene.Field(
        InstallationType,
        device_id=graphene.Int(required=True)
    )
    all = graphene.Field(
        AllDataType,
        serial=graphene.Float(required=True)
    )

    def resolve_installation(self, info, device_id):
        response = api_call('installations/?device=%s' % device_id)['results'][0]
        return json2obj(json.dumps(response))

    def resolve_all(self, info, serial):
        response = api_call('devices/?serial=%s' % serial)['results'][0]
        return json2obj(json.dumps(response))

The query I need to do is like this:

query {
    all(serial:201002000856){
        device{
            id
            serial
            reference
        }
        installation{
            company
            device
        }
    }
}

So, my problem is how to make a relation with this two types, as described in AllDataType, the resolve_installation needs a device id and resolve_all needs a serial number of device.

To resolve the installation I need the device id returned by resolve_all resolver.

How can I achieve this?

The resolve_ methods in Query need to return the right type of data, as defined in Query. For example, resolve_all should return an AllDataType object. So you'll need to take the results of your api_call method to build AllDataType and InstallationType objects. Here's an example with some made up methods to get the device and installation from the REST-fetched data:

def resolve_all(self, info, serial):
    response = api_call('devices/?serial=%s' % serial)['results'][0]
    # need to process the response to get the values you need
    device = get_device_from_response(response)
    installation = get_installation_from_response(response)
    return AllDataType(device=device, installation=installation)

You might also need to add resolve methods to your Type classes. There's an example here.