code: func (p *LogicalWindow) PredicatePushDown(predicates []expression.Expression) ([]expression.Expression, LogicalPlan) {
  	// Window function forbids any condition to push down.
  	p.baseLogicalPlan.PredicatePushDown(nil)
  	return predicates, p
  }
docs: // PredicatePushDown implements LogicalPlan PredicatePushDown interface.