Summary
-------
The `folder` cube allows to create a tree of categories and classify entities
as you're used to do in a file-system.

Usage
-----

Define the relation `filed_under` in the schema, object must
contain all entities which can be classified in a folder.

.. sourcecode:: python

  class missing_filed_under(RelationDefinition):
      name = 'filed_under'
      subject = ('ExtProject', 'Project', 'Card', 'File')
      object = 'Folder'


The `FoldersBox` shows the folders hierarchy as a tree view. It's not visible by
default (user can activate it using their preferences) but you can activate it
by default using the code snippet below:

.. sourcecode:: python

    from cubes.folder.views import FoldersBox
    # make the folders box visible by default
    FoldersBox.visible = True
