Computed index field for Sitecore that indexes ContentHub assetIDs

ContentHubCustomizations.config

<configuration xmlns:patch="http://www.sitecore.net/xmlconfig/"
			   xmlns:set="http://www.sitecore.net/xmlconfig/set/"
			   xmlns:role="http://www.sitecore.net/xmlconfig/role/">
  <sitecore>
  
    <contentSearch>
      <indexConfigurations>
        <defaultSolrIndexConfiguration type="Sitecore.ContentSearch.SolrProvider.SolrIndexConfiguration, Sitecore.ContentSearch.SolrProvider">
          <documentOptions type="Sitecore.ContentSearch.SolrProvider.SolrDocumentBuilderOptions, Sitecore.ContentSearch.SolrProvider">
            <fields hint="raw:AddComputedIndexField">
              <!-- Extracts ContentHub AssetIds from image fields -->
              <field fieldName="contenthub_assetids" type="MyProject.ContentSearch.ContentHubImagesComputedField, MyProject" returnType="stringCollection">
              </field>
            </fields>
          </documentOptions>
        </defaultSolrIndexConfiguration>
      </indexConfigurations>
    </contentSearch>

  </sitecore>
</configuration>

ContentHubImagesComputedField.cs

using System.Collections.Generic;
using System.Linq;
using System.Xml;
using Sitecore.ContentSearch;
using Sitecore.ContentSearch.ComputedFields;
using Sitecore.Data.Fields;
using Sitecore.Data.Items;

namespace MyProject.ContentSearch
{
	/// <summary>
	/// Extracts ContentHub AssetIDs from image fields
	/// </summary>
	public class ContentHubImagesComputedField : AbstractComputedIndexField
	{
		public ContentHubImagesComputedField(XmlNode configNode) : base(configNode)
		{
		}

		public override object ComputeFieldValue(IIndexable indexable)
		{
			Item item = indexable as SitecoreIndexableItem;

			if (item == null)
			{
				return null;
			}

			IEnumerable<Field> imageFields = item.Fields.Where(f => f.TypeKey == "image");

			if (!imageFields.Any())
			{
				return null;
			}

			List<string> assetIds = new List<string>();

			foreach (Field imageField in imageFields)
			{
				string assetId = ((ImageField)imageField).GetAttribute("stylelabs-content-id");

				if (!string.IsNullOrEmpty(assetId))
				{
					assetIds.Add(assetId);
				}
			}

			return assetIds.Any() ? assetIds : null;
		}
	}
}

ContentHubImagesSearchResultItem.cs

public class ContentHubImagesSearchResultItem : SearchResultItem
{
  [IndexField("contenthub_assetids")]
  public virtual IEnumerable<string> ContentHubAssetIds { get; set; }
}