docs: def initialize(self, size=0):
          """Initialize file on storage and truncate to given size."""
          fs, path = self._get_fs()
  
          # Required for reliably opening the file on certain file systems:
          if fs.exists(path):
              fp = fs.open(path, mode='r+b')
          else:
              fp = fs.open(path, mode='wb')
  
          try:
              fp.truncate(size)
          except Exception:
              fp.close()
              self.delete()
              raise
          finally:
              fp.close()
  
          self._size = size
  
          return self.fileurl, size, None