code: public boolean isAvailable(QualifiedName name) {
  		SymbolTable.Group group = symbolTable.get(name.getUnit());
  		return group != null && group.isAvailable(name.getName());
  	}
docs: Check whether a given symbol is currently external to the enclosing WyilFile.
  Specifically, this indicates whether or not a stub is available for it.
  
  @param name
  @return