def _replace_angle_brackets(url_string):
    """
    Replace angle brackets with braces in a given url.

    Swaggerhub prefers URLs with variables to have curly braces instead of
    angle brackets, so this replaces all instances of angle brackets with curly
    braces. For example:

    /users/<user_id> -> /users/{user_id}

    """
    return url_string.replace("<", "{").replace(">", "}")