The current crates.io release and git version of rustc-demangle fails to demangle symbols that make use of the vendor-specific suffix.
For example, the symbol _RNvNvNvCs7qp2U7fqm6G_7mycrate7EXAMPLE7___getit5___KEY$tlv$init does not get demangled by demangle_stream. Removing the $ suffix does make the demangling work, with the resulting symbol being mycrate::EXAMPLE::__getit::__KEY.