old_contents: # -*- coding: UTF8 -*-
  from pypeline.writers import Writer
  
  class FileWriter(Writer):
      def __init__(self, sink):
          self.sink = sink
  
      def __call__(self, content):
          open(self.sink).write(content)
  
new_contents: # -*- coding: UTF8 -*-
  from pypeline.writers import Writer
  
  class FileWriter(Writer):
      def __init__(self, sink):
          self.sink = sink
  
      def __call__(self, content):
          open(self.sink, 'a+').write(content)
  
subject: Add updating mode to the open instruction for FileWriter