input: Write a function to find the common elements between two given lists.
  assert find_common_elements([1, 2, 3], [2, 3, 4])==[2, 3]
  assert find_common_elements([4, 5, 6], [7, 8, 9])==[]
  assert find_common_elements([1, 1, 2, 3], [1, 3, 1, 3])==[1, 1, 3]
output: def find_common_elements(list1, list2):
      return [item for item in list1 if item in list2]