def graphql_union(name, description=None):
    """Annotate a static method or global function as a description of a union.

    Decorator that annotates a static method or global function as
    returning a list of the names of the types that comprise a GraphQL
    union type.  The types must be object, interface, and union types.
    At present, we do not support annotating a function with multiple
    graphql_union annotations.

    basestring name - The name of the union type.
    basestring description - A description of the type, or None.
        GraphQL favors the Markdown format.
    """
    def decorator(func):
        func._graphql_union_name = name
        func._graphql_union_description = description
        return func
    return decorator