input: Write a python function to return the current month and the previous month as a tuple.
  assert month_names() == ('October', 'September')
  assert month_names() == ('January', 'December')
  assert month_names() == ('March', 'February')
output: from datetime import datetime, timedelta
  
  def month_names():
      current_date = datetime.now()
      current_month = current_date.strftime('%B')
      previous_month_date = current_date.replace(day=1) - timedelta(days=1)
      previous_month = previous_month_date.strftime('%B')
      return (current_month, previous_month)