Function parse_or_schema_from 

pub fn parse_or_schema_from<T: FdlArgsTrait>(argv: &[String]) -> T

Slice-based variant of parse_or_schema. The first element is the program name (displayed in help text), the rest are arguments.

Used by the fdl driver itself when dispatching to sub-commands: each sub-command parses its own args[2..] tail without re-reading env::args.