Function is_valid_mrz_input 

pub fn is_valid_mrz_input(s: &str) -> bool

Utilities for MRZ-specific string operations: validation, trimming a specific character, and OCR-friendly character replacements commonly used when processing MRZ zones.

These functions are intentionally simple and avoid heap allocations where possible, but return owned String when a transformed string is required. Return true if s contains only valid MRZ characters: uppercase A-Z, digits 0-9, or the filler ‘<’.