input: Write a python function to count people in the age range 10-20 from two age groups.
  assert count_people_in_age_range([15, 22, 18, 9], [10, 21, 19]) == 3
  assert count_people_in_age_range([5, 12, 14], [20, 25, 17]) == 3
  assert count_people_in_age_range([8, 25, 30], [35, 45, 50]) == 0
output: def count_people_in_age_range(group1, group2):
      return sum(10 <= age <= 20 for age in group1 + group2)