code: func (p *SigningProfile) Usages() (ku x509.KeyUsage, eku []x509.ExtKeyUsage, unk []string) {
  	for _, keyUse := range p.Usage {
  		if kuse, ok := KeyUsage[keyUse]; ok {
  			ku |= kuse
  		} else if ekuse, ok := ExtKeyUsage[keyUse]; ok {
  			eku = append(eku, ekuse)
  		} else {
  			unk = append(unk, keyUse)
  		}
  	}
  	return
  }
docs: // Usages parses the list of key uses in the profile, translating them
  // to a list of X.509 key usages and extended key usages.  The unknown
  // uses are collected into a slice that is also returned.