input: Write a function to find the common elements between two given lists. If there are no common elements, return an empty list.
  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([3, 4, 5], [4, 5, 6])==[4, 5]
  assert find_common_elements([], [1, 2, 3])==[]
  assert find_common_elements([1, 2, 3], [])==[]
output: def find_common_elements(list1, list2):
      return list(set(list1) & set(list2))