new_contents: """
  Rectangular Brush
  =================
  This example shows how to add a simple rectangular brush to a scatter plot.
  By clicking and dragging on the plot, you can highlight points within the
  range.
  """
  
  import altair as alt
  from vega_datasets import data
  
  cars = data.cars.url
  brush = alt.selection(type='interval')
  
  chart = alt.Chart(cars).mark_point().encode(
      x='Horsepower:Q',
      y='Miles_per_Gallon:Q',
      color=alt.condition(brush, 'Cylinders:O', alt.ColorValue('grey'))
  ).properties(
      selection=brush
  )
  
subject: add interactive brush example