Moped 2.0.7 undefined method `session'

Question

I have no idea what's going on here. I upgraded to MOPED 2.0.7 and I'm getting this undefined method `session' for #

User.tags_index_collection
 => #<Moped::Collection:0x007fa744fe2c50 @database=#<Mongo::Database:0x70178196887520 name=my_mongo_development>, @name="users_tags_index"> 

Then according to their documentation here, I should be able to do:

User.tags_index_collection.find.entries

But when I do, I get

NoMethodError: undefined method `session' for #<Mongo::Database:0x007fa744fe2fc0>
    from /Users/me/.rvm/gems/ruby-2.3.0/gems/moped-2.0.7/lib/moped/query.rb:501:in `session'
    from /Users/me/.rvm/gems/ruby-2.3.0/gems/moped-2.0.7/lib/moped/query.rb:93:in `cursor'
    from /Users/me/.rvm/gems/ruby-2.3.0/gems/moped-2.0.7/lib/moped/query.rb:78:in `each'
    from (irb):8:in `entries'

Any ideas?