code: func (c *Collection) VisitAscend(pivot gtreap.Item, visitor gtreap.ItemVisitor) {
  	c.currentRoot().VisitAscend(pivot, visitor)
  }
docs: // VisitAscend traverses the Collection ascendingly, invoking visitor for each
  // visited item.
  //
  // If visitor returns false, iteration will stop prematurely.
  //
  // VisitAscend is a more efficient traversal than using an Iterator, and is
  // useful in times when entry-by-entry iteration is not required.