'Assign a registered instance to a custom layer. You cannot use
this action with instances that were created with AWS
OpsWorks.
**Required Permissions**: To use this action, an IAM user must
have a Manage permissions level for the stack or an attached
policy that explicitly grants permissions. For more
information on user permissions, see `Managing User
Permissions`_.
:type instance_id: string
:param instance_id: The instance ID.
:type layer_ids: list
:param layer_ids: The layer ID, which must correspond to a custom
layer. You cannot assign a registered instance to a built-in layer.'

def assign_instance(self, instance_id, layer_ids):

    params = {'InstanceId': instance_id, 'LayerIds': layer_ids}
    return self.make_request(action='AssignInstance', body=json.dumps(params))
