match.go
func (p *Part) DepthMatchFirst(matcher PartMatcher) *Part {
	root := p
	for {
		if matcher(p) {
			return p
		}
		c := p.FirstChild
		if c != nil {
			p = c
		} else {
			for p.NextSibling == nil {
				if p == root {
					return nil
				}
				p = p.Parent
			}
			p = p.NextSibling
		}
	}
}
func (p *Part) DepthMatchFirst(matcher PartMatcher) *Part {
	root := p
	for {
		if matcher(p) {
			return p
		}
		c := p.FirstChild
		if c != nil {
			p = c
		} else {
			for p.NextSibling == nil {
				if p == root {
					return nil
				}
				p = p.Parent
			}
			p = p.NextSibling
		}
	}
}
// DepthMatchFirst performs a depth first search of the Part tree and returns the first part that
// causes the given matcher to return true