input: Write a function to return a new list containing only the common elements between two input lists. 
  assert common_elements([1, 2, 3, 4, 8], [2, 6, 8, 10])==[2, 8]
  assert common_elements([1, 3, 5, 7], [2, 4, 6, 8])==[]
  assert common_elements([], [1, 2, 3])==[]
  assert common_elements(['a', 'b', 'c'], ['b', 'c', 'd'])==['b', 'c']
  assert common_elements([1, "apple", 3.5], ["apple", 3.5])==["apple", 3.5]
output: def common_elements(list1, list2):
      return [item for item in list1 if item in list2]