How to use the nbsphinx.NotebookParser function in nbsphinx

# Add any Sphinx extension module names here, as strings. They can be
# extensions coming with Sphinx (named 'sphinx.ext.*') or your custom
# ones.
extensions = [
    'sphinx.ext.mathjax',
]

# Add any paths that contain templates here, relative to this directory.
templates_path = ['_templates']

# The suffix(es) of source filenames.
# You can specify multiple suffix as a list of string:
source_suffix = ['.rst', '.ipynb']

source_parsers = {'ipynb': NotebookParser}

# The encoding of source files.
#source_encoding = 'utf-8-sig'

# The master toctree document.
master_doc = 'index'

# General information about the project.
project = u'Jupyter Notebook Tools for Sphinx'
author = u'Matthias Geier'
copyright = u'2015, ' + author

# The version info for the project you're documenting, acts as replacement for
# |version| and |release|, also used in various other places throughout the
# built documents.
#

dest_path = os.path.normpath(os.path.join(source_dir, dest_path))
        if os.path.exists(src_path):
            any_dirs = any_dirs or os.path.isdir(src_path)
            copy_and_register_files(src_path, dest_path, document)
        else:
            logger.warning(
                'The path "{}", defined in {} "extra-media", '
                'isn\'t a valid path.'.format(
                    extract_media_path, source_file
                )
            )
        if any_dirs:
            document.settings.env.note_reread()


class LinkedNotebookParser(NotebookParser):
    """A parser for .nblink files.

    The parser will replace the link file with the output from
    nbsphinx on the linked notebook. It will also add the linked
    file as a dependency, so that sphinx will take it into account
    when figuring out whether it should be rebuilt.

    The .nblink file is a JSON file with the following structure:

    {
        "path": "relative/path/to/notebook"
    }

    Optionally the "extra-media" key can be added, if your notebook includes
    any media, i.e. images. The value needs to be an array of strings,
    which are paths to the media files or directories.