code: def get_wd_data(self):
          
          wait = wx.BusyInfo('Reading in data from current working directory, please wait...')
          #wx.Yield()
          print('-I- Read in any available data from working directory')
          self.contribution = cb.Contribution(self.WD, dmodel=self.data_model)
          del wait
docs: Show dialog to get user input for which directory
          to set as working directory.
          Called by self.get_dm_and_wd