code: def InitLocCheck(self):
          
          # if there is a location without a name, name it 'unknown'
          self.contribution.rename_item('locations', 'nan', 'unknown')
          # propagate lat/lon values from sites table
          self.contribution.get_min_max_lat_lon()
          # propagate lithologies & geologic classes from sites table
          self.contribution.propagate_cols_up(['lithologies',
                                               'geologic_classes'], 'locations', 'sites')
          res = self.contribution.propagate_min_max_up()
          if cb.not_null(res):
              self.contribution.propagate_cols_up(['age_unit'], 'locations', 'sites')
  
          # set up frame
          self.panel = wx.Panel(self, style=wx.SIMPLE_BORDER)
          self.grid_frame = grid_frame3.GridFrame(self.contribution, self.WD,
                                                  'locations', 'locations', self.panel,
                                                  main_frame=self.main_frame)
          # redefine default 'save & exit grid' button to go to next dialog instead
          self.grid_frame.exitButton.SetLabel('Save and continue')
          grid = self.grid_frame.grid
          self.grid_frame.Bind(wx.EVT_BUTTON,
                               lambda event: self.onContinue(event, grid, self.InitAgeCheck),
                               self.grid_frame.exitButton)
          # add back button
          self.backButton = wx.Button(self.grid_frame.panel, id=-1, label='Back',
                                        name='back_btn')
          self.Bind(wx.EVT_BUTTON,
                    lambda event: self.onbackButton(event, self.InitSiteCheck),
                    self.backButton)
          self.grid_frame.main_btn_vbox.Add(self.backButton, flag=wx.ALL, border=5)
          # re-do fit
          self.grid_frame.do_fit(None, min_size=self.min_size)
          # center
          self.grid_frame.Centre()
          return
docs: make an interactive grid in which users can edit locations