IsTree
''''''

.. function:: IsTree(Graph)

Determines if *Graph* is a connected tree. The function returns a (boolean, int) tuple, where the boolean indicates whether *Graph* is a tree and the int is the node id for the root of the tree.

Parameters:

- *Graph*: directed graph (input) 
    A Snap.py directed graph or a network

Return value: 

- tuple 
    The tuple consists of a bool that indicates whether *Graph* is a tree, and an int giving the node id for the root of the tree.


The following example shows how to detect trees in 
:class:`TNGraph` and :class:`TNEANet`::

    import snap

    Graph = snap.GenTree(snap.PNGraph, 3, 3)
    (is_tree, root_id) = snap.IsTree(Graph)
    print "The graph is a tree: %s " % is_tree
    print "The graph has a root id: %d" % root_id

    Network = snap.GenTree(snap.PNEANet, 3, 3)
    (is_tree, root_id) = snap.IsTree(Network)
    print "The graph is a tree: %s " % is_tree
    print "The graph has a root id: %d" % root_id