'Get names of performance instances for a node.'

def get_performance_instance_names(self, object_name):

    api_args = {'objectname': object_name}
    result = self.send_request('perf-object-instance-list-info', api_args, enable_tunneling=False)
    instance_names = []
    instances = (result.get_child_by_name('instances') or netapp_api.NaElement('None'))
    for instance_info in instances.get_children():
        instance_names.append(instance_info.get_child_content('name'))
    return instance_names
