input: Write a function to find common elements between two lists.
  assert find_common_elements([2, 3, 5, 8], [1, 4, 5, 9])==[5]
  assert find_common_elements([1, 2, 3, 4], [3, 4, 5, 6])==[3, 4]
  assert find_common_elements([10, 20, 30], [40, 50, 60])==[]
output: def find_common_elements(list1, list2):
      return list(set(list1) & set(list2))