Function validate_tree 

pub fn validate_tree<'a, I>(paths: I) -> Result<(), TreeError>
where
    I: IntoIterator<Item = &'a RelativePath>,

Validates the cross-path rules of a module file tree.

Two checks are performed.

• The reserved filenames module.json, module-lock.json, and module.sig may appear only at the module root (i.e. as a single path component, not nested in any subdirectory).
• No two distinct paths may collapse to the same Unicode Normalization Form C (NFC).