'The node immediately following the invocant in their parent\'s children
list. If the invocant does not have a next sibling, it is None'

@property
def next_sibling(self):

    if (self.parent is None):
        return
    else:
        for (i, child) in enumerate(self.parent.children):
            if (child is self):
                try:
                    return self.parent.children[(i + 1)]
                except IndexError:
                    return
        return
