Implement class walker.

def visit_ClassDef(self, node):
        """Implement class walker."""
        # [[[cog
        # cog.out("print(pcolor('Enter class visitor', 'magenta'))")
        # ]]]
        # [[[end]]]
        # Get class information (name, line number, etc.)
        element_full_name = self._pop_indent_stack(node, "class")
        code_id = (self._fname, node.lineno)
        self._processed_line = node.lineno
        # Add class entry to dictionaries
        self._class_names.append(element_full_name)
        self._callables_db[element_full_name] = {
            "name": element_full_name,
            "type": "class",
            "code_id": code_id,
            "last_lineno": None,
        }
        self._reverse_callables_db[code_id] = element_full_name
        # [[[cog
        # code = """
        # print(
        #     pcolor(
        #         'Visiting class {0} @ {1}, indent = {2}'.format(
        #             element_full_name, code_id[1], self._get_indent(node)
        #         ),
        #         'green'
        #     )
        # )
        # """
        # cog.out(code)
        # ]]]
        # [[[end]]]
        self.generic_visit(node)