code: def _DrawHours(self):
      
      tmpstrs = []
      for i in range(0, self._gwidth, self._min_grid):
        if i % self._hour_grid == 0:
          tmpstrs.append('<polyline class="FullHour" points="%d,%d, %d,%d" />' \
                         % (i + .5 + 20, 20, i + .5 + 20, self._gheight))
          tmpstrs.append('<text class="Label" x="%d" y="%d">%d</text>'
                         % (i + 20, 20,
                           (i / self._hour_grid + self._offset) % 24))
        else:
          tmpstrs.append('<polyline class="SubHour" points="%d,%d,%d,%d" />' \
                         % (i + .5 + 20, 20, i + .5 + 20, self._gheight))
      return "".join(tmpstrs)
docs: Generates svg to show a vertical hour and sub-hour grid
  
      Returns:
        # A string containing a polyline tag for each grid line
        " <polyline class="FullHour" points="20,0 ..."