code: def get_file_size(self, fid):
          
          url = self.get_file_url(fid)
          res = self.conn.head(url)
          if res is not None:
              size = res.headers.get("content-length", None)
              if size is not None:
                  return int(size)
          return None
docs: Gets size of uploaded file
          Or None if file doesn't exist.
  
          Args:
              **fid**: File identifier <volume_id>,<file_name_hash>
  
          Returns:
              Int or None