def _insert_extensions(c):
    """Insert the ``extensions`` variable into the configuration state.
    """
    c['extensions'] = ['sphinx.ext.autodoc', 'sphinx.ext.doctest',
        'sphinx.ext.intersphinx', 'sphinx.ext.todo', 'sphinx.ext.coverage',
        'sphinx.ext.mathjax', 'sphinx.ext.ifconfig', 'sphinxcontrib.jinja',
        'sphinx-prompt', 'sphinxcontrib.autoprogram', 'numpydoc',
        'sphinx_automodapi.automodapi', 'sphinx_automodapi.smart_resolver',
        'breathe', 'sphinx_click.ext', 'documenteer.sphinxext',
        'documenteer.sphinxext.lssttasks']
    return c
