input: Write a function to find the common elements between two lists and return a new list containing only those common elements. If the input lists are empty, return an empty list.
  assert common_elements([1, 2, 3, 4, 8], [2, 6, 8, 10])==[2, 8]
  assert common_elements([5, 6, 7], [1, 3, 5, 7, 9])==[5, 7]
  assert common_elements([1, 2, 3], [4, 5, 6])==[]
  assert common_elements([], [1, 2, 3])==[]
  assert common_elements([], [])==[]
output: def common_elements(list1, list2):
      return list(set(list1) & set(list2))