input: Write a function to find the common elements between two lists. If there are common elements between the two lists, return them as a new list. If there are no common elements, return an empty list. The function should take two lists as input and return a list containing the common elements.
  assert find_common_elements([3, 9, 15, 21, 27], [21, 7, 13, 29, 31]) == [21]
  assert find_common_elements([3, 9, 15], [21, 7, 13]) == []
  assert find_common_elements([], [21, 7, 13]) == []
  assert find_common_elements([3, 9, 15, 21, 7], [7, 3]) == [3, 7]
  assert find_common_elements([1, 2, 3], [3, 2, 1]) == [1, 2, 3]
output: def find_common_elements(list1, list2):
      return list(set(list1) & set(list2))