\param Module a module object.
\returns the parent of a sub-module or NULL if the given module is top-level, e.g. for 'std.vector' it will return the 'std' module.
See Implementation
\param Module a module object.
\returns the parent of a sub-module or NULL if the given module is top-level, e.g. for 'std.vector' it will return the 'std' module.