Read data for molecule_number from filename of type file_type, beginning with timestep nb, ending with timestep ne, with a stride of ns+1. Return the number of timesteps read from this file; if the file contains more than this number, the remaining timesteps will be loaded during subsequent VMD display updates. By default, one timestep will be loaded before the command returns. New in VMD 1.8: The waitfor option allows you to specify how many timesteps to load before returning. The waitfor parameter nw can be any integer, or all; choosing nw less than zero is the same as choosing all. If timesteps from other files are still being loaded when the animate command is issued, these timesteps will be loaded first.