def METHOD_NAME(name):
    """
    Create a new environment called ``name``, but do not set it as the
    current environment.
    :raises: ``ValueError`` if an environment with name ``name``
             already exists.
    """
    if name in list(__environments.keys()):
        msg = "Environment {} already exists".format(name)
        raise ValueError(msg)
    __environments[name] = []