How to read Odata service(created for SAP LOB) response which is a entity query set and expects filter parameters, in SharePoint BCS code?

I am performing DUET development where in the requirement is to read collection of data(attachments in SAP) is published over OData service by Gateway development. It is filtering based on 3 parameters but the method created for ReadAllAttachments inside BDCM is not having any "IN" parameter so that I can pass them via arguments as below.

entity.Execute(createMethodInstance, lobSystemInstance, ref arguments);

Since above code works fine for read single data. But I am looking for reading collection of data which is created in SAP gateway as entity(query) not entity(read) and expecting a input filters but not having any "IN" parameter as part of BDCM file creation. Now, question is How do I read this collection from Odata service which has attachments from SAP and I have to pass filter parameters ex: UserID, TravelNo etc.. but there is no "IN" parameter? Anyone pointing to a reference or provide me a code snippet will help. Thank you in advance. - Raghav