Resources update function results in Python HTTP request InvalidSchema error

I am calling nexussdk.resources.update on a resource created on Nexus sandbox (nexus-sandbox.io), and the function results in HTTP request results in InvalidSchema error: "No connection adapters were found for 'base:?rev=1'"

Here is the instance object that is used to send the request:

OrderedDict([('@context', ['https://nexus-sandbox.io/v1/resources/kcnitest/redcap/_/medredcontexttest10']), ('@id', 'initial_appointmen_arm_1'), ('_self', 'base:initial_appointmen_arm_1'), ('_constrainedBy', 'https://bluebrain.github.io/nexus/schemas/unconstrained.json'), ('_project', 'https://nexus-sandbox.io/v1/projects/kcnitest/redcap'), ('_rev', 1), ('_deprecated', False), ('_createdAt', '2019-02-12T15:53:26.937Z'), ('_createdBy', 'https://nexus-sandbox.io/v1/realms/github/users/ehsanmaag'), ('_updatedAt', '2019-02-12T15:53:26.937Z'), ('_updatedBy', 'https://nexus-sandbox.io/v1/realms/github/users/ehsanmaag'), ('title', 'Initial Appointment'), ('medred:includesInstrument', ['ex:patient_health_questionnaire_9'])])

It seems the reason is that instance["_self"] does not contain the full request URL.
How can we resolve that?

nexussdk.resources.update から開始し、issue に示されているインスタンスオブジェクトを使ってリクエストを再現します。_self の値、特に base:initial_appointmen_arm_1 形式がどのようにリクエスト URL になるかを追跡します。Nexus sandbox で作成されたリソースの更新で InvalidSchema が発生しなくなれば完了です。

索引モデルが issue の本文から書いたものです。