If we have a ContentType like so:

publicclassMyContentType{publicIEnumable<MyPropertyType>MyPropertyTypeList{get;set;}}

and we use the graph source client:

_graphSourceClient.ConfigureContentType<MyContentType>().Field(f=>f.MyPropertyTypeList,IndexingType.PropertyType)

when the client is generating the type definition through
SourceConfigurationModel method AddContentTypeField

It will add to the fieldConfiguration for the MappedTypeIEnumerable`1
Instead of [MyPropertyType]