title: A timer event for dash in Python
body: <p>I am using Dash to build a GUI for sending data to a remote server.
  The update process is asynchronic - as the data could take time to load.
  After the user presses a button on the dash GUI it saves the data on the remote server as a CSV file, and once the file is saved it tells the server (using an API) to start running the upload process.
  I would like to show the user the progress of the upload using a callback that will fire every 5 seconds.
  I couldn't find any documentation on Dash's web site regarding this type of callback.
  Is there any method for firing a callback every X seconds?</p>