How to bind variables inside collection literals in Cassandra using Scala?

Question

I am trying to bind data to map type column in Cassandra using my Spark Scala application.

val updateTemplate = s"""UPDATE test_ks.test_table_ttl USING TTL 5
                 |SET ttl_col = ttl_col + {:mapKey : (':value1', ':value2')}
                 |WHERE consumer_id=:consumer_id""".stripMargin
val prep_statement: PreparedStatement = cqlSession.prepare(updateTemplate)

This is throwing an error.

Invalid map literal for ttl_col: bind variables are not supported inside collection literals

My DDL for Cassandra table is like this.

CREATE KEYSPACE test_ks
WITH replication = {'class':'SimpleStrategy', 'replication_factor' : 3};

CREATE TABLE test_ks.test_table_ttl (
    consumer_id TEXT PRIMARY KEY,
    ttl_col map<text, frozen<tuple<text, text>>>
);