# Method Stdio.NonblockingStream()->set_fs_event_callback()

Method set_fs_event_callback

  `NonblockingStream set_read_callback(function(:void) f, mixed ... rest)`
  `NonblockingStream set_write_callback(function(:void) f, mixed ... rest)`
  `NonblockingStream set_close_callback(function(:void) f, mixed ... rest)`
  `NonblockingStream set_fs_event_callback(function(:void) f, int event_mask, mixed ... rest)`