code: def _prepare_domain(mapping):
          
          # Parse the domain-directory mapping
          try:
              domain, dir = mapping.split(':')
          except ValueError:
              print("Please provide the sources in the form of '<domain>:<directory>'")
              sys.exit(1)
  
          try:
              default_language = settings.TRANSLATION_DOMAINS[domain]
          except KeyError:
              print("Unknown domain {domain}, check the settings file to make sure"
                    " this domain is set in TRANSLATION_DOMAINS".format(domain=domain))
              sys.exit(1)
          # Create a temporary file to hold the `.pot` file for this domain
          handle, path = tempfile.mkstemp(prefix='zengine_i18n_', suffix='.pot')
          return (domain, {
              'default': default_language,
              'pot': path,
              'source': dir,
          })
docs: Prepare a helper dictionary for the domain to temporarily hold some information.