[autopep8] added autopep8 as an example of lib usage

README_autopep8.md

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+Python code prettifying unsing autopep8
+=======================================
+
+This extension reformats/prettifies code in a notebook's code cell, uniquely for python language, using the autopep8 package.
+
+Under the hood, it uses the KerneExecOnCells library, shared with `code_prettify`and  `2to3`
+The nbextension provides
+
+- a toolbar button (configurable to be added or not)
+- a keyboard shortcut for reformatting the current code-cell (default shortcut
+  is `Alt-A`, can also be configured not to add the keyboard shortcut).
+- a keyboard shortcut for reformatting the whole notebook (default shortcut
+  is `Alt-Shift-A`, can also be configured not to add the keyboard shortcut).
+Syntax shall be correct. The nbextension will also point basic syntax errors.
+
+prerequisites
+-------------
+
+Of course, you must have the necessary kernel-specific packages installed for
+the prettifier call to work:
+
+- for the default python implementation, the
+  [autopep8](https://github.com/hhatto/autopep8) module is required:
+
+      pip install autopep8
+
+  Others you might consider using include [autopep8](https://github.com/hhatto/autopep8).

autopep8.js

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+// Copyright (c) Jupyter-Contrib Team.
+// Distributed under the terms of the Modified BSD License.
+// Authors: @kenkoooo, @jfbercher and @jcb91
+
+define(function(require, exports, module) {
+    'use strict';
+
+    var kernel_exec_on_cell = require('./kernel_exec_on_cell');
+
+    var mod_name = 'autopep8';
+
+    // gives default settings
+    var cfg = {
+        add_toolbar_button: true,
+        hotkeys: {
+            process_selected: 'Alt-A',
+            process_all: 'Alt-Shift-A',
+        },
+        register_hotkey: true,
+        show_alerts_for_errors: true,
+        button_icon: 'fa-cog',
+        button_label: 'Prettify (using autopep8)',
+        kbd_shortcut_text: 'Prettify' // ' current cell(s)'
+    };
+
+    cfg.kernel_config_map = { // map of parameters for supported kernels
+        "python": {
+            "library": "import json\nimport autopep8",
+            "prefix": "print(json.dumps(autopep8.fix_code(u",
+            "postfix": ")))"
+        }
+    };
+
+    var prettifier = new kernel_exec_on_cell.define_plugin(mod_name, cfg);
+    prettifier.load_ipython_extension = prettifier.initialize_plugin;
+    return prettifier;
+
+    });

autopep8.yaml

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+Type: Jupyter Notebook Extension
+Name: Autopep8
+Description: Use kernel-specific code to reformat/prettify the contents of code cells
+Link: README_autopep8.md
+Main: autopep8.js
+Compatibility: Jupyter (4.x)
+Parameters:
+
+- name: autopep8.add_toolbar_button
+  description: Add a toolbar button to prettify the selected cell(s)
+  input_type: checkbox
+  default: true
+
+- name: autopep8.button_icon
+  description: |
+    Toolbar button icon: afont-awesome class defining the icon used for the
+    toolbar button and actions.
+    See http://fontawesome.io/icons/ for available icons.
+  input_type: text
+  default: 'fa-cog'
+
+- name: autopep8.button_label
+  description: Toolbar button label text
+  input_type: text
+  default: 'Code prettify'
+
+- name: autopep8.register_hotkey
+  description: |
+    Register hotkeys to prettify the selected code cell(s), or all code cells
+    in the notebook
+  input_type: checkbox
+  default: true
+
+- name: autopep8.hotkeys.process_selected
+  description: Hotkey to use to prettify the selected cell(s)
+  input_type: hotkey
+  default: 'Alt-A'
+
+- name: autopep8.hotkeys.process_all
+  description: Hotkey to use to prettify the whole notebook
+  input_type: hotkey
+  default: 'Alt-Shift-A'
+
+- name: autopep8.show_alerts_for_errors
+  description: Show alerts for errors in the kernel prettifying calls
+  input_type: checkbox
+  default: true
+
+- name: autopep8.kernel_config_map_json
+  description: |
+    json object defining library calls required to load the kernel-specific
+    prettifying modules, and the prefix & postfix for the json-format string
+    required to make the prettifying call.
+  input_type: json_object
+  default: |
+    {
+        "python": {
+            "library": "import json\nimport autopep8",
+            "prefix": "print(json.dumps(autopep8.fix_code(u",
+            "postfix": ")))"
+        }
+    }