The parser/unparse.py file lacks functions to handle the `Str`, `Num`, `Bytes` and `NameConstant` types.

Can we add them since it seems to be simple enough?

These types are obsolete. The compiler never generates an AST tree containing them.

Okay. 

But can lines like

    if first:first = False
    else: self.write(", ")

be changed to span across more number of lines?

Because things like

    first:first

looks like a type hint.

> be changed to span across more number of lines?
Yes, that changed in ast._Unparser, and i agree with Serhiy. There is no need for supporting that old constant nodes. IMHO this issue can be closed

We usually do not accept cosmetic changes. If these lines be changed for other reasons (fixing a bug, adding new feature), their style can be changed.