.CompletedProcess: ClassType
.CompletedProcess.
    args: Str or [Str; _]
    returncode: Int
    stdout: Bytes or NoneType
    stderr: Bytes or NoneType

.run!: (
    args: Str or [Str; _],
    stdin: File! or NoneType := NoneType,
    stdout: File! or NoneType := NoneType,
    stderr: File! or NoneType := NoneType,
    capture_output := Bool,
    shell := Bool,
) => .CompletedProcess
.call!: (
    args: Str or [Str; _],
    stdin: File! or NoneType := NoneType,
    stdout: File! or NoneType := NoneType,
    stderr: File! or NoneType := NoneType,
    shell := Bool,
) => Int
.check_call!: (
    args: Str or [Str; _],
    stdin: File! or NoneType := NoneType,
    stderr: File! or NoneType := NoneType,
    shell := Bool,
) => {0} or Never
.check_output!: (
    args: Str or [Str; _],
    stdin: File! or NoneType := NoneType,
    stderr: File! or NoneType := NoneType,
    shell := Bool,
) => Bytes or NoneType