How to use the pyflakes.messages.UndefinedName function in pyflakes

global_scope_index = 1 if self._in_doctest() else 0
        global_scope = self.scopeStack[global_scope_index]

        # Ignore 'global' statement in global scope.
        if self.scope is not global_scope:

            # One 'global' statement can bind multiple (comma-delimited) names.
            for node_name in node.names:
                node_value = Assignment(node_name, node)

                # Remove UndefinedName messages already reported for this name.
                # TODO: if the global is not used in this scope, it does not
                # become a globally defined name.  See test_unused_global.
                self.messages = [
                    m for m in self.messages if not
                    isinstance(m, messages.UndefinedName) or
                    m.message_args[0] != node_name]

                # Bind name to global scope if it doesn't exist already.
                global_scope.setdefault(node_name, node_value)

                # Bind name to non-global scopes, but as already "used".
                node_value.used = (global_scope, node)
                for scope in self.scopeStack[global_scope_index + 1:]:
                    scope[node_name] = node_value

global_scope_index = 1 if self._in_doctest() else 0
        global_scope = self.scopeStack[global_scope_index]

        # Ignore 'global' statement in global scope.
        if self.scope is not global_scope:

            # One 'global' statement can bind multiple (comma-delimited) names.
            for node_name in node.names:
                node_value = Assignment(node_name, node)

                # Remove UndefinedName messages already reported for this name.
                # TODO: if the global is not used in this scope, it does not
                # become a globally defined name.  See test_unused_global.
                self.messages = [
                    m for m in self.messages if not
                    isinstance(m, messages.UndefinedName) or
                    m.message_args[0] != node_name]

                # Bind name to global scope if it doesn't exist already.
                global_scope.setdefault(node_name, node_value)

                # Bind name to non-global scopes, but as already "used".
                node_value.used = (global_scope, node)
                for scope in self.scopeStack[global_scope_index + 1:]:
                    scope[node_name] = node_value

global_scope_index = 1 if self._in_doctest() else 0
        global_scope = self.scopeStack[global_scope_index]

        # Ignore 'global' statement in global scope.
        if self.scope is not global_scope:

            # One 'global' statement can bind multiple (comma-delimited) names.
            for node_name in node.names:
                node_value = Assignment(node_name, node)

                # Remove UndefinedName messages already reported for this name.
                # TODO: if the global is not used in this scope, it does not
                # become a globally defined name.  See test_unused_global.
                self.messages = [
                    m for m in self.messages if not
                    isinstance(m, messages.UndefinedName) or
                    m.message_args[0] != node_name]

                # Bind name to global scope if it doesn't exist already.
                global_scope.setdefault(node_name, node_value)

                # Bind name to non-global scopes, but as already "used".
                node_value.used = (global_scope, node)
                for scope in self.scopeStack[global_scope_index + 1:]:
                    scope[node_name] = node_value

# mark '*' imports as used for each scope
                        binding.used = (self.scope, node)
                        from_list.append(binding.fullName)

            # report * usage, with a list of possible sources
            from_list = ', '.join(sorted(from_list))
            self.report(messages.ImportStarUsage, node, name, from_list)
            return

        if name == '__path__' and os.path.basename(self.filename) == '__init__.py':
            # the special name __path__ is valid only in packages
            return

        # protected with a NameError handler?
        if 'NameError' not in self.exceptHandlers[-1]:
            self.report(messages.UndefinedName, node, name)

# mark '*' imports as used for each scope
                        binding.used = (self.scope, node)
                        from_list.append(binding.fullName)

            # report * usage, with a list of possible sources
            from_list = ', '.join(sorted(from_list))
            self.report(messages.ImportStarUsage, node, name, from_list)
            return

        if name == '__path__' and os.path.basename(self.filename) == '__init__.py':
            # the special name __path__ is valid only in packages
            return

        # protected with a NameError handler?
        if 'NameError' not in self.exceptHandlers[-1]:
            self.report(messages.UndefinedName, node, name)

"""
        # In doctests, the global scope is an anonymous function at index 1.
        global_scope_index = 1 if self.withDoctest else 0
        global_scope = self.scopeStack[global_scope_index]

        # Ignore 'global' statement in global scope.
        if self.scope is not global_scope:

            # One 'global' statement can bind multiple (comma-delimited) names.
            for node_name in node.names:
                node_value = Assignment(node_name, node)

                # Remove UndefinedName messages already reported for this name.
                self.messages = [
                    m for m in self.messages if not
                    isinstance(m, messages.UndefinedName) and not
                    m.message_args[0] == node_name]

                # Bind name to global scope if it doesn't exist already.
                global_scope.setdefault(node_name, node_value)

                # Bind name to non-global scopes, but as already "used".
                node_value.used = (global_scope, node)
                for scope in self.scopeStack[global_scope_index + 1:]:
                    scope[node_name] = node_value

"""
        # In doctests, the global scope is an anonymous function at index 1.
        global_scope_index = 1 if self.withDoctest else 0
        global_scope = self.scopeStack[global_scope_index]

        # Ignore 'global' statement in global scope.
        if self.scope is not global_scope:

            # One 'global' statement can bind multiple (comma-delimited) names.
            for node_name in node.names:
                node_value = Assignment(node_name, node)

                # Remove UndefinedName messages already reported for this name.
                self.messages = [
                    m for m in self.messages if not
                    isinstance(m, messages.UndefinedName) and not
                    m.message_args[0] == node_name]

                # Bind name to global scope if it doesn't exist already.
                global_scope.setdefault(node_name, node_value)

                # Bind name to non-global scopes, but as already "used".
                node_value.used = (global_scope, node)
                for scope in self.scopeStack[global_scope_index + 1:]:
                    scope[node_name] = node_value

scope[name].used = (self.scope, node)
            except KeyError:
                pass
            else:
                return

        # look in the built-ins
        if importStarred or name in self.builtIns:
            return
        if name == '__path__' and os.path.basename(self.filename) == '__init__.py':
            # the special name __path__ is valid only in packages
            return

        # protected with a NameError handler?
        if 'NameError' not in self.exceptHandlers[-1]:
            self.report(messages.UndefinedName, node, name)

def handleNodeDelete(self, node):
        name = getNodeName(node)
        if not name:
            return
        if isinstance(self.scope, FunctionScope) and name in self.scope.globals:
            self.scope.globals.remove(name)
        else:
            try:
                del self.scope[name]
            except KeyError:
                self.report(messages.UndefinedName, node, name)