Yes, you'll be able to refer to it via the 'b' object.
If you've mapped it then you can refer to the mapped name by u.data.[name].
e.g. if you may 'example_data_source' to 'test' then you could refer to it as 'b.example_data_source' or 'u.data.test'
Mapping to in custom containers is very powerful. You might want to read this post to learn a bit more about the power of custom containers:
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