def _insert_intersphinx_mapping(c):
    """Insert the ``intersphinx_mapping``, ``intersphinx_timeout`` and
    ``intersphinx_cache_limit`` variableis into the configuration state.
    """
    c['intersphinx_mapping'] = {'python': ('https://docs.python.org/3/',
        None), 'numpy': ('https://docs.scipy.org/doc/numpy/', None),
        'scipy': ('https://docs.scipy.org/doc/scipy/reference/', None),
        'matplotlib': ('https://matplotlib.org/', None), 'sklearn': (
        'https://scikit-learn.org/stable/', None), 'pandas': (
        'https://pandas.pydata.org/pandas-docs/stable/', None), 'astropy':
        ('http://docs.astropy.org/en/v3.0.x/', None),
        'astro_metadata_translator': (
        'https://astro-metadata-translator.lsst.io', None),
        'firefly_client': ('https://firefly-client.lsst.io', None)}
    c['intersphinx_timeout'] = 10.0
    c['intersphinx_cache_limit'] = 5
    return c
