sometimes make private names available

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Within a single package, sometimes names beginning with underscores are things that need to be imported internally; implementation modules might be private. So if I'm working in src/foo/_bar.py and _baz is defined in src/foo/_qux.py, I want to see that import available. However, not all private symbols should be indexed; if I'm in src/xyz, I should not see any private imports from foo/.