Returns
		-------
		altair.Chart

def make_chart(self):
		'''
		Returns
		-------
		altair.Chart
		'''
		task_df = self.get_task_df()
		import altair as alt
		chart = alt.Chart(task_df).mark_bar().encode(
			x='start',
			x2='end',
			y='term',
		)
		return chart