def find_root(self):
        self.find_parents()
        index = 0
        while len(self.vertices[index].parents)>0:
            index = self.vertices[index].parents[0]
        return index
Finds the index of the root node of the tree.
dataset/ETHPy150Open SheffieldML/GPy/GPy/util/mocap.py/tree.find_root