Showcase mixin tests fail for Ads templates

[parthea]

See build log here where the mixin tests fail for Ads templates in PR https://github.com/googleapis/gapic-generator-python/pull/2175

See stack trace below

tests/system/test_mixins.py:75: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
/tmp/tmpdpiecome/google/showcase/v1beta1/services/echo/client.py:1521: in get_location
    self._transport.get_location,
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

self = <google.showcase.v1beta1.services.echo.transports.rest.EchoRestTransport object at 0x7f63c5f9bb50>

    @property
    def get_location(self,
    ) -> Callable[
        [locations_pb2.GetLocationRequest],
        Union[locations_pb2.Location, Awaitable[locations_pb2.Location]],
    ]:
>       raise NotImplementedError()
E       NotImplementedError

/tmp/tmpdpiecome/google/showcase/v1beta1/services/echo/transports/base.py:367: NotImplementedError
__________________________ test_list_locations[rest] ___________________________

echo = <google.showcase.v1beta1.services.echo.client.EchoClient object at 0x7f63c5fe3310>

    def test_list_locations(echo):
        response = echo.list_locations(
            {
>               "name": "projects/some_project",
            }
        )

tests/system/test_mixins.py:84: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
/tmp/tmpdpiecome/google/showcase/v1beta1/services/echo/client.py:1572: in list_locations
    self._transport.list_locations,
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

self = <google.showcase.v1beta1.services.echo.transports.rest.EchoRestTransport object at 0x7f63c5f9ea10>

    @property
    def list_locations(self,
    ) -> Callable[
        [locations_pb2.ListLocationsRequest],
        Union[locations_pb2.ListLocationsResponse, Awaitable[locations_pb2.ListLocationsResponse]],
    ]:
>       raise NotImplementedError()
E       NotImplementedError

/tmp/tmpdpiecome/google/showcase/v1beta1/services/echo/transports/base.py:375: NotImplementedError