docs: def prevparent(self, parent, depth):
          '''
          Subtract lines from our curline if the name of a node is prefixed with
          the parent directory when traversing the grandparent object.
          '''
          pdir = os.path.dirname(self.name)
          if depth > 1:  # can't jump to parent of root node!
              for c, d in parent.traverse():
                  if c.name == self.name:
                      break
                  if c.name.startswith(pdir):
                      parent.curline -= 1
          else:  # otherwise jus skip to previous directory
              pdir = self.name
              # - 1 otherwise hidden parent node throws count off & our
              # self.curline doesn't change!
              line = -1
              for c, d in parent.traverse():
                  if c.name == self.name:
                      break
                  if os.path.isdir(c.name) and c.name in parent.children[0:]:
                      parent.curline = line
                  line += 1
          return pdir