def get_folder(stub_config, datacenter_name, folder_name):
    """
    Returns the identifier of a folder
    Note: The method assumes that there is only one folder and datacenter
    with the mentioned names.
    """
    datacenter = datacenter_helper.get_datacenter(stub_config, datacenter_name)
    if not datacenter:
        print("Datacenter '{}' not found".format(datacenter_name))
        return None

    filter_spec = Folder.FilterSpec(type=Folder.Type.VIRTUAL_MACHINE,
                                    names=set([folder_name]),
                                    datacenters=set([datacenter]))

    folder_svc = Folder(stub_config)
    folder_summaries = folder_svc.list(filter_spec)
    if len(folder_summaries) > 0:
        folder = folder_summaries[0].folder
        print("Detected folder '{}' as {}".format(folder_name, folder))
        return folder
    else:
        print("Folder '{}' not found".format(folder_name))
        return None