Hide certain implementation specific classes/variables

[lzchen]

Fixes #1640

[codeboten]

LGTM

[ocelotl]

Why remove the documentation? It is very possible that this documentation applies for all implementations of this abstract method.

Also this:

from abc import ABC, abstractmethod
from inspect import getdoc


class Parent(ABC):
    @abstractmethod
    def method(self):
        """
        The documentation for method
        """


class Child(Parent):

    def method(self):
        pass


print(getdoc(Child().method))

The documentation for method

[lzchen]

Since _RuntimeContext is used internally, we do not expect anyone to inherit it and implement a context on their own. As well, since we are hiding the class via protected, the documentation will not show up in readthedocs anyways.

[aabmass]

Still nice to have for us so if you mouse a call site, IDEs will show the docstring

[lzchen]

Sure, I added to both.

[ocelotl]

I still think it would be convenient to keep the documentation since there will be classes that will inherit from this one, but this is pretty much a nit, so approving.