'Requests a description of a specified set of apps.
You must specify at least one of the parameters.
**Required Permissions**: To use this action, an IAM user must
have a Show, Deploy, or 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 stack_id: string
:param stack_id: The app stack ID. If you use this parameter,
`DescribeApps` returns a description of the apps in the specified
stack.
:type app_ids: list
:param app_ids: An array of app IDs for the apps to be described. If
you use this parameter, `DescribeApps` returns a description of the
specified apps. Otherwise, it returns a description of every app.'

def describe_apps(self, stack_id=None, app_ids=None):

    params = {}
    if (stack_id is not None):
        params['StackId'] = stack_id
    if (app_ids is not None):
        params['AppIds'] = app_ids
    return self.make_request(action='DescribeApps', body=json.dumps(params))
