code: func (p *Signing) Valid() bool {
  	if p == nil {
  		return false
  	}
  
  	log.Debugf("validating configuration")
  	if !p.Default.validProfile(true) {
  		log.Debugf("default profile is invalid")
  		return false
  	}
  
  	for _, sp := range p.Profiles {
  		if !sp.validProfile(false) {
  			log.Debugf("invalid profile")
  			return false
  		}
  	}
  
  	p.warnSkippedSettings()
  
  	return true
  }
docs: // Valid checks the signature policies, ensuring they are valid
  // policies. A policy is valid if it has defined at least key usages
  // to be used, and a valid default profile has defined at least a
  // default expiration.