code: def combine(a1, a2):
      ''' Combine to argument into a single flat list
  
      It is used when you are not sure whether arguments are lists but want to combine them into one flat list
  
      Args:
          a1: list or other thing
          a2: list or other thing
  
      Returns:
          list: a flat list contain a1 and a2
      '''
      if not isinstance(a1, list):
          a1 = [a1]
      if not isinstance(a2, list):
          a2 = [a2]
      return a1 + af combine(a1, a2):
      ''' Combine to argument into a single flat list
  
      It is used when you are not sure whether arguments are lists but want to combine them into one flat list
  
      Args:
          a1: list or other thing
          a2: list or other thing
  
      Returns:
          list: a flat list contain a1 and a2
      '''
      if not isinstance(a1, list):
          a1 = [a1]
      if not isinstance(a2, list):
          a2 = [a2]
      return a1 + a2
docs: Combine to argument into a single flat list
  
      It is used when you are not sure whether arguments are lists but want to combine them into one flat list
  
      Args:
          a1: list or other thing
          a2: list or other thing
  
      Returns:
          list: a flat list contain a1 and a2