Function source_looks_like_cim_dist 

pub fn source_looks_like_cim_dist(source: &Source) -> bool

Whether a source holds distribution CIM: its own buffer reads as distribution CIM (looks_like_cim_dist), or, for a directory, one of the .xml documents at its top level does. The reads go through the source, so they count against its acquisition budget and are cached for the parse that follows.