input: Write a function to calculate number of days between two dates.
  assert getNumberOfDays(date(2020, 8, 18), date(2020, 9, 1)) == 14
  assert getNumberOfDays(date(2021, 1, 1), date(2021, 1, 31)) == 30
  assert getNumberOfDays(date(2019, 12, 25), date(2020, 1, 1)) == 7
output: from datetime import date
  
  def getNumberOfDays(start_date, end_date):
      return (end_date - start_date).days