def METHOD_NAME(cls):
    # type: () -> Bootstrap
    """Locates the active PEX bootstrap.
    :rtype: :class:`Bootstrap`
    """
    if cls._INSTANCE is None:
        bootstrap_path = __file__
        module_import_path = __name__.split(".")
        # For example, our __file__ might be requests.pex/.bootstrap/pex/bootstrap.pyc and our import
        # path pex.bootstrap; so we walk back through all the module components of our import path to
        # find the base sys.path entry where we were found (requests.pex/.bootstrap in this example).
        for _ in module_import_path:
            bootstrap_path = os.path.dirname(bootstrap_path)
        cls._INSTANCE = cls(sys_path_entry=bootstrap_path)
    return cls._INSTANCE