input: Write a function to take two lists as input and return a new list containing only the common elements between the two input lists. If there are no common elements, return an empty list.
  def common_elements(list1, list2):
      common_list=[]
      for element in list1:
          if element in list2:
              common_list.append(element)
      return common_list
  assert common_elements([1, 2, 3, 4, 8], [2, 6, 8, 10])==[2, 8]
  assert common_elements([1, 2, 3], [4, 5, 6])==[]
  assert common_elements([], [1, 2, 3])==[]
  assert common_elements([1, 2, 3], [])==[]
output: def common_elements(list1, list2):
      common_list=[]
      for element in list1:
          if element in list2:
              common_list.append(element)
      return common_list