POST with nested properties

[BpStef]

I'm trying to do a POST with the Simple OData Client to my API but when we try to do this I get:
'The property 'Producer' does not exist on type 'Waste.QualificationsCore.API.Interface.OData.Qualifications.QualificationDto'. Make sure to only use property names that are defined by the type or mark the type as open type.'

The code the POST is:
return await _client.For<QualificationDto>(ODataPath(Paths.ODataV1Qualifications)) .Set(request) .InsertEntryAsync(token);

The DTO I'm trying to add is:
` public class QualificationDto
{
[Key]
public Guid QualificationId { get; set; }

	[NonFilterable]
	[NotFilterable]
	public DateTime? DocumentDate { get; set; }

	[NonFilterable]
	[NotFilterable]
	public DateTime? ExpiryDate { get; set; }

	public string IdentificationCode { get; set; }

	[AutoExpand]
	public ProducerDto Producer { get; set; }

}`

The Producer is a reference to an object in another datasource so I want to show it as an seperate object and not an ID. (e.g. Owned type on EF).

How can I fix/do this?