input: Write a function to find common elements between two lists and return a new list containing only these common elements. If there are no common elements, return an empty list. 
  
  assert common_elements([1, 2, 3, 4, 8], [2, 6, 8, 10]) == [2, 8]
  assert common_elements([1, 3, 5], [2, 4, 6]) == []
  assert common_elements([], [1, 2, 3]) == []
  assert common_elements([1, 2, 3], [3, 2, 1]) == [1, 2, 3]
  assert common_elements([5, 5, 5, 5], [5, 5]) == [5, 5]
output: def common_elements(list1, list2):
      return list(set(list1) & set(list2))