input: Write a function to find the common elements between two given lists. If there are no common elements, return an empty list. If either of the lists is empty, return an empty list as well.
  assert find_common_elements([1, 2, 3], [2, 3, 4])==[2, 3]
  assert find_common_elements([1, 2, 3], [4, 5, 6])==[]
  assert find_common_elements([1, 2, 3], [])==[]
  assert find_common_elements([], [4, 5, 6])==[]
  assert find_common_elements([], [])==[]
output: def find_common_elements(list1, list2):
      if not list1 or not list2:
          return []
      return list(set(list1) & set(list2))