input: Write a python function to find common elements between two lists.
  assert common_elements([1, 2, 3, 4], [3, 4, 5, 6]) == [3, 4]
  assert common_elements([10, 20, 30], [5, 10, 15, 20]) == [10, 20]
  assert common_elements(['apple', 'banana', 'cherry'], ['cherry', 'date', 'apple']) == ['apple', 'cherry']
output: def common_elements(list1, list2):
      return list(set(list1) & set(list2))