code: def get_availabilities_for_duration(duration, availabilities):
      
      duration_availabilities = []
      start_time = '10:00'
      while start_time != '17:00':
          if start_time in availabilities:
              if duration == 30:
                  duration_availabilities.append(start_time)
              elif increment_time_by_thirty_mins(start_time) in availabilities:
                  duration_availabilities.append(start_time)
  
          start_time = increment_time_by_thirty_mins(start_time)
  
      return duration_availabilities
docs: Helper function to return the windows of availability of the given duration, when provided a set of 30 minute windows.