def get_object_defaults(object_schema):
    """
    Extracts default values dict (nested) from an type object schema.

    :param object_schema: Schema type object
    :type  object_schema: dict
    :returns: Nested dict with defaults values
    """
    default = {}
    for k, schema in object_schema.get('properties', {}).items():

        if schema.get('type') == 'object':
            if 'default' in schema:
                default[k] = schema['default']

            try:
                object_defaults = get_object_defaults(schema)
            except NoObjectDefaults:
                if 'default' not in schema:
                    raise NoObjectDefaults
            else:
                if 'default' not in schema:
                    default[k] = {}

                default[k].update(object_defaults)
        else:
            if 'default' in schema:
                default[k] = schema['default']

    if default:
        return default

    raise NoObjectDefaults