data = pd.DataFrame({
    'a': list('CCCDDDEEE'),
    'b': [2, 7, 4, 1, 2, 6, 8, 4, 7]
})
spec = alt.Chart(data).mark_point().encode(
    x='a',
    y='b'
)
chart = AltairChart(title='Scientific Proof')
chart.set_data(spec)

class SciChart(AltairChart):
    title = 'Scientific Proofiness'

    def load(self):
        data = pd.DataFrame({
            'a': list('CCCDDDEEE'),
            'b': [2, 7, 4, 1, 2, 6, 8, 4, 10]
        })
        spec = alt.Chart(data).mark_point().encode(
            x='a',
            y='b'
        )
        self.set_data(spec)