# In addition to the parent and children associations, the following instance methods are added to the class
# after calling <tt>acts_as_tree</tt>:
# * <tt>siblings</tt> - Returns all the children of the parent, excluding the current node (<tt>[subchild2]</tt> when called on <tt>subchild1</tt>)
# * <tt>self_and_siblings</tt> - Returns all the children of the parent, including the current node (<tt>[subchild1, subchild2]</tt> when called on <tt>subchild1</tt>)
# * <tt>ancestors</tt> - Returns all the ancestors of the current node (<tt>[child1, root]</tt> when called on <tt>subchild2</tt>)
# * <tt>root</tt> - Returns the root of the current node (<tt>root</tt> when called on <tt>subchild2</tt>)
moduleClassMethods
# Configuration options are:
#
# * <tt>foreign_key</tt> - specifies the column name to use for tracking of the tree (default: +parent_id+)
# * <tt>order</tt> - makes it possible to sort the children according to this SQL snippet.
# * <tt>counter_cache</tt> - keeps a count in a +children_count+ column if set to +true+ (default: +false+).