human
Solve the following python programming problem given the following code:
@directive('resources')
def resource(**kwargs):
assistant
#Here is the Python code you requested.

    """Define an external resource to be fetched and staged when building the
    package. Based on the keywords present in the dictionary the appropriate
    FetchStrategy will be used for the resource. Resources are fetched and
    staged in their own folder inside spack stage area, and then moved into
    the stage area of the package that needs them.
    List of recognized keywords:
    * \when\ : (optional) represents the condition upon which the resource is
    needed
    * \destination\ : (optional) path where to move the resource. This path
    must be relative to the main package stage area.
    * \placement\ : (optional) gives the possibility to fine tune how the
    resource is moved into the main package stage area.
    """
    def _execute(pkg):
        when = kwargs.get('when', pkg.name)
        destination = kwargs.get('destination', '')
        placement = kwargs.get('placement', None)
        if os.path.isabs(destination):
            message = 'The    destination    keyword    of    a    resource    directive    '
            "can't    be    an    absolute    path.\n"
            message += " DCTB destination    :    '{dest}\n'".format(dest=destination)
            raise RuntimeError(message)
        test_path = 'stage_folder_root'
        normalized_destination = os.path.normpath(join_path(test_path, destination))
        if (test_path not in normalized_destination):
            message = 'The    destination    folder    of    a    resource    must    fall    '
            'within    the    main    package    stage    directory.\n'
            message += " DCTB destination    :    '{dest}'\n".format(dest=destination)
            raise RuntimeError(message)
        when_spec = parse_anonymous_spec(when, pkg.name)
        resources = pkg.resources.setdefault(when_spec, [])
        name = kwargs.get('name')
        fetcher = from_kwargs(**kwargs)
        resources.append(Resource(name, fetcher, destination, placement))
    return _execute