Memorizes a function/class/module docstring

def _onDocstring( self, docstr, line ):
        " Memorizes a function/class/module docstring "
        if self.objectsStack:
            self.objectsStack[ -1 ].docstring = \
                                 Docstring( trim_docstring( docstr ), line )
            return

        self.docstring = Docstring( trim_docstring( docstr ), line )
        return