class_docstr: A setting to be used to display directories and their files
  
  The FileCollectionDisplay shows directory trees with mechanisms to
  communicate directory additions and deletions to its parent module.
  
  The central data structure is the dictionary, "self.file_tree". The keys
  for the top-level of the dictionary are the directories managed by the
  setting. If a key represents a directory, its value is another directory.
  If a key represents a file, its value is either True (the file is included
  in the collection) or False (the file is filtered out of the collection).
  
  Directory dictionaries can be filtered: this is done by setting the
  special key, "None" to either True or False.
  
  The FileCollectionDisplay manages the tree and it should be treated as
  read-only by callers. Callers can request that nodes be added, removed,
  filtered or not filtered by calling the appropriate notification function
  with a nested collection of two-tuples and strings (modpaths). Two-tuples
  represent directories whose subdirectories or files are being operated on.
  Strings represent directories or files that are being operated on. The first
  element of the two-tuple is the directory name and the second is a
  sub-collection of two-tuples. For instance, to operate on foo/bar, send:
  
  ("foo", ("bar", ))
  
  The FileCollectionDisplay communicates events on individual files or
  directories by specifying a path as a collection of path parts. These
  can be any sort of object and it is the caller's job to maintain the
  display names of each of them and their node categories (used for
  icon display).
code: def get_show_filtered(self):
      return self.properties[self.SHOW_FILTERED]
  
imports: import json
  from ._setting import Setting
label_desc: Use image node_id 20 for calling the FileCollectionDisplay obj's underlying member method code with example usage: obj.get_show_filtered() and returns: self