Determine the URL corresponding to Python object
    This code is from
    https://github.com/numpy/numpy/blob/master/doc/source/conf.py#L290
    and https://github.com/Lasagne/Lasagne/pull/262

def linkcode_resolve(domain, info):
    """
    Determine the URL corresponding to Python object
    This code is from
    https://github.com/numpy/numpy/blob/master/doc/source/conf.py#L290
    and https://github.com/Lasagne/Lasagne/pull/262
    """
    if domain != 'py':
        return None

    modname = info['module']
    fullname = info['fullname']

    submod = sys.modules.get(modname)
    if submod is None:
        return None

    obj = submod
    for part in fullname.split('.'):
        try:
            obj = getattr(obj, part)
        except:
            return None

    try:
        fn = inspect.getsourcefile(obj)
    except:
        fn = None
    if not fn:
        return None

    try:
        source, lineno = inspect.getsourcelines(obj)
    except:
        lineno = None

    if lineno:
        linespec = "#L%d-L%d" % (lineno, lineno + len(source) - 1)
    else:
        linespec = ""

    filename = info['module'].replace('.', '/')
    return "http://github.com/allenai/allennlp/blob/master/%s.py%s" % (filename, linespec)