Test whether this instance exists.

        See
        https://cloud.google.com/spanner/reference/rpc/google.spanner.admin.instance.v1#google.spanner.admin.instance.v1.InstanceAdmin.GetInstanceConfig

        :rtype: bool
        :returns: True if the instance exists, else false

def exists(self):
        """Test whether this instance exists.

        See
        https://cloud.google.com/spanner/reference/rpc/google.spanner.admin.instance.v1#google.spanner.admin.instance.v1.InstanceAdmin.GetInstanceConfig

        :rtype: bool
        :returns: True if the instance exists, else false
        """
        api = self._client.instance_admin_api
        metadata = _metadata_with_prefix(self.name)

        try:
            api.get_instance(self.name, metadata=metadata)
        except NotFound:
            return False

        return True