Function store_is_valid_path 

pub unsafe extern "C" fn store_is_valid_path(
    context: *mut c_context,
    store: *mut Store,
    path: *const StorePath,
) -> bool

@brief Check if a StorePath is valid (i.e. that corresponding store object and its closure of references exists in the store) @param[out] context Optional, stores error information @param[in] store Nix Store reference @param[in] path Path to check @return true or false, error info in context