old_contents: 
  
  
  
  
  
  class BAM2BED(object):
  
      def __init__(self, filename):
          pass
  
      def __call__(self):
          pass
  
new_contents: 
  
  
  
  
  
  class BED2BAM(object):
      """
  
  
      """
      def __init__(self, infile, outfile=None, *args, **kwargs):
          """.. rubric:: constructor
  
          :param str filename
          """
          pass
  
      def __call__(self):
          pass
  
  
  
  
subject: define common API