Feature proposal: `rbs todo` command

[ksss]

Problem

Finding missing RBS definitions

Identifying which RBS definitions are missing is a difficult and painstaking task.
The person writing the RBS does not know what the missing RBS is.

Make sure the RBS is practical.

The RBS writer is not confident in the RBS described.
The only way is to start the type checker (steep) and try to write the source code.

Feature proposal: rbs todo command

rbs todo command display a list of unimplemented methods.

When check for unimplemented methods in the IO class.

$ rbs todo IO
- def pread
- def pwrite
- def to_path
...

Yet another way: rbs prototype runtime --todo

--todo option acts like a filter to display only methods that are not yet implemented in defined RBS.

$ rbs prototype runtime --todo IO
class IO
  def pread: (*untyped) -> untyped
  def pwrite: (untyped, untyped) -> untyped
  def to_path: () -> untyped
end