code: func (f *Field) bsiGroup(name string) *bsiGroup {
  	f.mu.RLock()
  	defer f.mu.RUnlock()
  	for _, bsig := range f.bsiGroups {
  		if bsig.Name == name {
  			return bsig
  		}
  	}
  	return nil
  }
docs: // bsiGroup returns a bsiGroup by name.