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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_announce_filename( working_dir ):
 """ Get the path to the file that stores all of the announcements. """

   announce_filepath = os.path.join( working_dir, get_default_virtualchain_impl().get_virtual_chain_name() ) + '.announce'
   return announce_filepath