code: func (p *deviceFolderDownloadState) Has(file string, version protocol.Vector, index int32) bool {
  	p.mut.RLock()
  	defer p.mut.RUnlock()
  
  	local, ok := p.files[file]
  
  	if !ok || !local.version.Equal(version) {
  		return false
  	}
  
  	for _, existingIndex := range local.blockIndexes {
  		if existingIndex == index {
  			return true
  		}
  	}
  	return false
  }
docs: // Has returns whether a block at that specific index, and that specific version of the file
  // is currently available on the remote device for pulling from a temporary file.