input: Write a function that takes two lists as input and returns a new list containing only the common elements between the two lists. 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, 2, 2, 3], [2, 2, 3, 4]) == [2, 2, 3]
  assert common_elements([1, 3, 5], [2, 4, 6]) == []
  assert common_elements([], [1, 2, 3]) == []
  assert common_elements([4, "cat", 6], ["cat", 4, 6]) == [4, "cat", 6]
output: def common_elements(list1, list2):
      return [item for item in list1 if item in list2]