input: Write a function to remove all the duplicates from a linked list.
  
  def remove_duplicates(self, list_nodes):
      curr_node= self.head 
      new_list=[]
      while curr_node != None: 
          if curr_node.data not in new_list: 
              new_list.append(curr_node.data) 
          curr_node = curr_node.next
              
      # creating a linked list from the unique elements of list_nodes  
      self.head=None
      for i in new_list:
          self.insert_node(i)
  
  assert remove_duplicates([7, 14, 28, 28, 28, 35, 49]) == [7, 14, 28, 35, 49]
output: def remove_duplicates(self, list_nodes):
      curr_node = self.head
      new_list = []
      while curr_node != None:
          if curr_node.data not in new_list:
              new_list.append(curr_node.data)
          curr_node = curr_node.next
              
      self.head = None
      for i in new_list:
          self.insert_node(i)