code: def _msgmerge(po_path, pot_file, backup):
      
      pot_file.seek(0)
      command = [
          'msgmerge',
          '--update',
          '--width=200',
          '--backup=%s' % ('simple' if backup else 'off'),
          po_path,
          '-'
      ]
      p3 = Popen(command, stdin=pot_file)
      p3.communicate()
docs: Merge an existing .po file with new translations.
  
      :arg po_path: path to the .po file
      :arg pot_file: a file-like object for the related templates
      :arg backup: whether or not to create backup .po files