<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def zoom_in(self):
 """Increase zoom factor and redraw TimeLine"""

        index = self._zoom_factors.index(self._zoom_factor)
        if index + 1 == len(self._zoom_factors):
            # Already zoomed in all the way
            return
        self._zoom_factor = self._zoom_factors[index + 1]
        if self._zoom_factors.index(self.zoom_factor) + 1 == len(self._zoom_factors):
            self._button_zoom_in.config(state=tk.DISABLED)
        self._button_zoom_out.config(state=tk.NORMAL)
        self.draw_timeline()