new_contents: """
  Cumulative Count Chart
  ----------------------
  This example shows an area chart with cumulative count.
  Adapted from https://vega.github.io/vega-lite/examples/area_cumulative_freq.html
  
  """
  # category: area charts
  
  import altair as alt
  from vega_datasets import data
  
  source = data.movies.url
  
  alt.Chart(source).transform_window(
      cumulative_count="count(count)",
      sort=[{"field": "IMDB_Rating"}],
  ).mark_area().encode(
      x="IMDB_Rating:Q",
      y="cumulative_count:Q"
  )
  
subject: Add example - Cumulative count