code: def from_buffer(self, buf):
          
          with self.lock:
              try:
                  # if we're on python3, convert buf to bytes
                  # otherwise this string is passed as wchar*
                  # which is not what libmagic expects
                  if isinstance(buf, str) and str != bytes:
                      buf = buf.encode('utf-8', errors='replace')
                  return maybe_decode(magic_buffer(self.cookie, buf))
              except MagicException as e:
                  return self._handle509Bug(e)
docs: Identify the contents of `buf`