code: def unroot(self):
          
          if len(self.children)==2:
              if not self.children[0].is_leaf():
                  self.children[0].delete()
              elif not self.children[1].is_leaf():
                  self.children[1].delete()
              else:
                  raise TreeError("Cannot unroot a tree with only two leaves")
docs: Unroots current node. This function is expected to be used on
          the absolute tree root node, but it can be also be applied to
          any other internal node. It will convert a split into a
          multifurcation.