Reduce visibility for internal components

[allenporter]

Is your feature request related to a problem? Please describe.
At the moment internal components are exposed the same way external/public components are exposed. Instead, the surface area of internal components should be reduced to avoid unexpected dependencies.

Describe the solution you'd like
Likely using the __all__ methods? we can decide what should be exposed and what should remain private.

Describe alternatives you've considered
Alternative could be to do nothing, but it may result in many breaking changes as internal APIs change.