Row level security with multiple roles

Thank you v-jiascu-msft.

Currently, for generatingtoken with single role i am passing the post request body as 

$clientid = "2";

{
"accessLevel": "View",
"identities": [
{
"username": $clientid ,
"roles": [ "Client" ],
"datasets": [ "9b61d620-e6ac-41fc-b2c9-3f1d89241a03" ]
}
]
}

Another field that comes in now is 

$location = "3";//Can be multiple location under client

Note: I may have multiple location under single client [under client 2 i may have location id 2,3,4 etc] and i have 2 different table called Clients and Locations. 

In Bi desktop i have Client role created as client_id = USERNAME(); (I have duplicated client id column as string)

How i can pass the location for username property of identities, where it takes single value?

What can be done at the power bi desktop to create the roles for both clients and locations ?

Thanks and regards

Pallavi