input: Write a python function to calculate the number of days in a month.
  assert num_days_in_month("February", 2020) == 29
  assert num_days_in_month("April", 2021) == 30
  assert num_days_in_month("December", 2019) == 31
output: def num_days_in_month(month, year):
      if month == "February":
          if (year % 4 == 0 and year % 100 != 0) or (year % 400 == 0):
              return 29
          else:
              return 28
      elif month in ["April", "June", "September", "November"]:
          return 30
      else:
          return 31