old_contents: """
  Stack module
  """
  __author__ = 'Taha Zerrouki taha.zerrouki@gmail.com'
  __license__ = 'GPL'
  __copyright__ = ['Arabtechies',  'Arabeyes',   'Taha Zerrouki']
  
  class Stack :
      """
  	Stack class
      """
      def __init__(self, text="") :
          """
          create a stack
          """
          self.items = list(text)
  
      def push(self, item) :
          """
          puch an item into the stack
          @param item: pushed item
          @type item : mixed
          @return : None
          @rtype: None
          """
          self.items.append(item)
  
      def pop(self) :
          """
          pop an item from the stack
          @return : poped item
          @rtype: mixed
          """
          if not self.is_empty():
              return self.items.pop()
          else:
              return None
  
      def is_empty(self) :
          """
          test if the stack is empty
          @return : True or False
          @rtype: boolean
          """
          return (self.items == [])
  
new_contents: """Stack module
  
  Includes code written by 'Arabtechies', 'Arabeyes', 'Taha Zerrouki'.
  """
  
  __author__ = ['Taha Zerrouki taha.zerrouki@gmail.com']
  __license__ = 'GPL'
  
  class Stack :
      """
  	Stack class
      """
      def __init__(self, text="") :
          """
          create a stack
          """
          self.items = list(text)
  
      def push(self, item) :
          """
          puch an item into the stack
          @param item: pushed item
          @type item : mixed
          @return : None
          @rtype: None
          """
          self.items.append(item)
  
      def pop(self) :
          """
          pop an item from the stack
          @return : poped item
          @rtype: mixed
          """
          if not self.is_empty():
              return self.items.pop()
          else:
              return None
  
      def is_empty(self) :
          """
          test if the stack is empty
          @return : True or False
          @rtype: boolean
          """
          return (self.items == [])
  
subject: Update stack.py