human
Solve the following python programming problem given the following code:
@not_implemented_for('directed')
def to_nested_tuple(T, root, canonical_form=False):
assistant
#Here is the Python code you requested.

    """Returns a nested tuple representation of the given tree.
    The nested tuple representation of a tree is defined
    recursively. The tree with one node and no edges is represented by
    the empty tuple, ``()``. A tree with ``k`` subtrees is represented
    by a tuple of length ``k`` in which each element is the nested tuple
    representation of a subtree.
    Parameters
    T : NetworkX graph
    An undirected graph object representing a tree.
    root : node
    The node in ``T`` to interpret as the root of the tree.
    canonical_form : bool
    If ``True``, each tuple is sorted so that the function returns
    a canonical form for rooted trees. This means "lighter" subtrees
    will appear as nested tuples before "heavier" subtrees. In this
    way, each isomorphic rooted tree has the same nested tuple
    representation.
    Returns
    tuple
    A nested tuple representation of the tree.
    Notes
    This function is *not* the inverse of :func:`from_nested_tuple`; the
    only guarantee is that the rooted trees are isomorphic.
    See also
    from_nested_tuple
    to_prufer_sequence
    Examples
    The tree need not be a balanced binary tree::
    >>> T = nx.Graph()
    >>> T.add_edges_from([(0, 1), (0, 2), (0, 3)])
    >>> T.add_edges_from([(1, 4), (1, 5)])
    >>> T.add_edges_from([(3, 6), (3, 7)])
    >>> root = 0
    >>> nx.to_nested_tuple(T, root)
    Continuing the above example, if ``canonical_form`` is ``True``, the
    nested tuples will be sorted::
    >>> nx.to_nested_tuple(T, root, canonical_form=True)
    Even the path graph can be interpreted as a tree::
    >>> T = nx.path_graph(4)
    >>> root = 0
    >>> nx.to_nested_tuple(T, root)
    """
    def _make_tuple(T, root, _parent):
        'Recursively    compute    the    nested    tuple    representation    of    the\n                                given    rooted    tree.\n\n                                ``_parent``    is    the    parent    node    of    ``root``    in    the    supertree    in\n                                which    ``T``    is    a    subtree,    or    ``None``    if    ``root``    is    the    root    of\n                                the    supertree.    This    argument    is    used    to    determine    which\n                                neighbors    of    ``root``    are    children    and    which    is    the    parent.\n\n                                '
        children = (set(T[root]) - {_parent})
        if (len(children) == 0):
            return ()
        nested = (_make_tuple(T, v, root) for v in children)
        if canonical_form:
            nested = sorted(nested)
        return tuple(nested)
    if (not nx.is_tree(T)):
        raise nx.NotATree('provided    graph    is    not    a    tree')
    if (root not in T):
        raise nx.NodeNotFound('Graph    {}    contains    no    node    {}'.format(T, root))
    return _make_tuple(T, root, None)