input: Write a python function to remove duplicates from a DataFrame and order it by date in descending order.
  assert removeDuplicates(df).collect() == expected_output  # Adjust 'df' and 'expected_output' to your test cases
  assert removeDuplicates(another_df).collect() == another_expected_output  # Adjust 'another_df' and 'another_expected_output' to your test cases
output: def removeDuplicates(df):
      df = df.drop_duplicates()
      df = df.orderBy("date", ascending=False)
      return df