code: func (s PluginMetaSet) ValidateVersions() (valid, invalid PluginMetaSet) {
  	valid = make(PluginMetaSet)
  	invalid = make(PluginMetaSet)
  	for p := range s {
  		if _, err := p.Version.Parse(); err == nil {
  			valid.Add(p)
  		} else {
  			invalid.Add(p)
  		}
  	}
  	return
  }
docs: // ValidateVersions returns two new PluginMetaSets, separating those with
  // versions that have syntax-valid semver versions from those that don't.
  //
  // Eliminating invalid versions from consideration (and possibly warning about
  // them) is usually the first step of working with a meta set after discovery
  // has completed.