def update(self, **kwargs):
        '''
        :param applet: ID of the applet to replace the app's contents with
        :type applet: string
        :param details: Metadata to store with the app (optional)
        :type details: dict or list
        :param access: Access specification (optional)
        :type access: dict
        :param resources: Specifies what is to be put into the app's resources container. Must be a string containing a project ID, or a list containing object IDs. (optional)
        :type resources: string or list

        Updates the parameters of an existing app. See the API
        documentation for the `/app/update
        <https://wiki.dnanexus.com/API-Specification-v1.0.0/Apps#API-method%253A-%252Fapp-xxxx%255B%252Fyyyy%255D%252Fupdate>`_
        method for more info.

        The current user must be a developer of the app.

        '''
        updates = {}
        for field in 'applet', 'billing', 'access', 'resources', 'details':
            if field in kwargs:
                updates[field] = kwargs[field]
                del kwargs[field]

        if self._dxid is not None:
            resp = dxpy.api.app_update(self._dxid, input_params=updates, **kwargs)
        else:
            resp = dxpy.api.app_update('app-' + self._name, alias=self._alias,
                                       input_params=updates, **kwargs)
:param applet: ID of the applet to replace the app's contents with
        :type applet: string
        :param details: Metadata to store with the app (optional)
        :type details: dict or list
        :param access: Access specification (optional)
        :type access: dict
        :param resources: Specifies what is to be put into the app's resources container. Must be a string containing a project ID, or a list containing object IDs. (optional)
        :type resources: string or list

        Updates the parameters of an existing app. See the API
        documentation for the `/app/update
        <https://wiki.dnanexus.com/API-Specification-v1.0.0/Apps#API-method%253A-%252Fapp-xxxx%255B%252Fyyyy%255D%252Fupdate>`_
        method for more info.

        The current user must be a developer of the app.