Auto inventory plugins not working

Manually, the playbook runs fine using a configuration yaml file for an autoplugin.
But not using node-ansible.
I'm using the cwd option to set /mypath_to_playbook.

Error: [WARNING]: * Failed to parse /mypath_to_playbook/import_constants.yaml with
auto plugin: must be str, not NoneType
[WARNING]: * Failed to parse /mypath_to_playbook/import_constants.yaml with
yaml plugin: Plugin configuration YAML file, not YAML inventory
[WARNING]: * Failed to parse /mypath_to_playbook/import_constants.yaml with
ini plugin: Invalid host pattern '---' supplied, '---' is normally a sign this
is a YAML file.
[WARNING]: Unable to parse /mypath_to_playbook/import_constants.yaml as an
inventory source
[WARNING]: No inventory was parsed, only implicit localhost is available

my code :
console.log("preping ansible command");
var command = new Ansible.Playbook().playbook('create_volume')
command.variables({ ... my extra vars ... });
command.inventory("import_constants.yaml")
console.log("executing ansible command");
var promise = command.exec({cwd:"/mypath_to_playbook"});