old_contents: from __future__ import print_function
  class Node:#create a Node
      def __int__(self,data):
          self.data=data#given data
          self.next=None#given next to None
  class Linked_List:
      
      pass
      
      def insert_tail(Head,data):
          if(Head.next is None):
              Head.next = Node(data)
          else:
              insert_tail(Head.next, data)
  
      def insert_head(Head,data):
          tamp = Head
          if (tamp == None):
              newNod = Node()#create a new Node
              newNod.data = data
              newNod.next = None
              Head = newNod#make new node to Head       
          else:
              newNod = Node()
              newNod.data = data
              newNod.next = Head#put the Head at NewNode Next
              Head=newNod#make a NewNode to Head
          return Head   
      
      def printList(Head):#print every node data
          tamp=Head
          while tamp!=None:
              print(tamp.data)
              tamp=tamp.next
      
      def delete_head(Head):#delete from head
          if Head!=None:
              Head=Head.next
          return Head#return new Head
      
      def delete_tail(Head):#delete from tail
          if Head!=None:
              tamp = Node()
              tamp = Head
              while (tamp.next).next!= None:#find the 2nd last element
                  tamp = tamp.next
              tamp.next=None#delete the last element by give next None to 2nd last Element
          return Head
  
      def isEmpty(Head):
          return Head is None #Return if Head is none
      
      def reverse(Head):
          prev = None
          current = Head
          
          while(current):
              # Store the current node's next node. 
              next_node = current.next
              # Make the current node's next point backwards
              current.next = prev
              # Make the previous node be the current node
              prev = current
              # Make the current node the next node (to progress iteration)
              current = next_node
          # Return prev in order to put the head at the end 
          Head = prev
  
new_contents: from __future__ import print_function
  
  
  class Node:  # create a Node
      def __int__(self, data):
          self.data = data  # given data
          self.next = None  # given next to None
  
  
  class Linked_List:
      def insert_tail(Head, data):
          if(Head.next is None):
              Head.next = Node(data)
          else:
              Head.next.insert_tail(data)
  
      def insert_head(Head, data):
          tamp = Head
          if tamp is None:
              newNod = Node()  # create a new Node
              newNod.data = data
              newNod.next = None
              Head = newNod  # make new node to Head
          else:
              newNod = Node()
              newNod.data = data
              newNod.next = Head  # put the Head at NewNode Next
              Head = newNod  # make a NewNode to Head
          return Head
  
      def printList(Head):  # print every node data
          tamp = Head
          while tamp is not None:
              print(tamp.data)
              tamp = tamp.next
  
      def delete_head(Head):  # delete from head
          if Head is not None:
              Head = Head.next
          return Head  # return new Head
  
      def delete_tail(Head):  # delete from tail
          if Head is not None:
              tamp = Node()
              tamp = Head
              while (tamp.next).next is not None:  # find the 2nd last element
                  tamp = tamp.next
              # delete the last element by give next None to 2nd last Element
              tamp.next = None
          return Head
  
      def isEmpty(Head):
          return Head is None  # Return if Head is none
  
      def reverse(Head):
          prev = None
          current = Head
  
          while(current):
              # Store the current node's next node.
              next_node = current.next
              # Make the current node's next point backwards
              current.next = prev
              # Make the previous node be the current node
              prev = current
              # Make the current node the next node (to progress iteration)
              current = next_node
          # Return prev in order to put the head at the end
          Head = prev
  
subject: Fix unresolved name: insert_tail()