Python,Kivy BoxLayoutのエラー？

Pycharmを使用してKivyでボタンを三つ作成したいのですが、エラーがでてしまいます。
親切なかたどれをどのようにすれば直せばいいのか教えていただけないでしょうか。

python
1from kivy.app import App
2from kivy.uix.button import Button
3from kivy.uix.boxlayout import BoxLayout
4
5class LayoutApp(App):
6    def build(self):
7     layout = BoxLayout(orientation='horizontal')
8     b1 = Button(text='Basic')
9     b2 = Button(text='MetaFile use')
10     b3 = Button(text='Deep Learning')
11     layout.add.widget(b1)
12     layout.add.widget(b2)
13     layout.add.widget(b3)
14     return layout
15
16LayoutApp().run()
17コード

C:\Users\daisu\anaconda3\python.exe C:/Users/daisu/PycharmProjects/untitled/analy0225
[INFO   ] [Logger      ] Record log in C:\Users\daisu.kivy\logs\kivy_20-03-01_1.txt
[INFO   ] [deps        ] Successfully imported "kivy_deps.gstreamer" 0.2.0
[INFO   ] [deps        ] Successfully imported "kivy_deps.glew" 0.2.0
[INFO   ] [deps        ] Successfully imported "kivy_deps.sdl2" 0.2.0
[INFO   ] [Kivy        ] v1.11.1
[INFO   ] [Kivy        ] Installed at "C:\Users\daisu\anaconda3\lib\site-packages\kivy\__init__.py"
[INFO   ] [Python      ] v3.7.4 (default, Aug  9 2019, 18:34:13) [MSC v.1915 64 bit (AMD64)]
[INFO   ] [Python      ] Interpreter at "C:\Users\daisu\anaconda3\python.exe"
[INFO   ] [Factory     ] 184 symbols loaded
[INFO   ] [Image       ] Providers: img_tex, img_dds, img_sdl2, img_pil, img_gif (img_ffpyplayer ignored)
[INFO   ] [Text        ] Provider: sdl2
[INFO   ] [Window      ] Provider: sdl2
[INFO   ] [GL          ] Using the "OpenGL" graphics system
[INFO   ] [GL          ] GLEW initialization succeeded
[INFO   ] [GL          ] Backend used <glew>
[INFO   ] [GL          ] OpenGL version <b'4.6.0 - Build 26.20.100.7262'>
[INFO   ] [GL          ] OpenGL vendor <b'Intel'>
[INFO   ] [GL          ] OpenGL renderer <b'Intel(R) UHD Graphics 620'>
[INFO   ] [GL          ] OpenGL parsed version: 4, 6
[INFO   ] [GL          ] Shading version <b'4.60 - Build 26.20.100.7262'>
[INFO   ] [GL          ] Texture max size <16384>
[INFO   ] [GL          ] Texture max units <32>
[INFO   ] [Window      ] auto add sdl2 input provider
[INFO   ] [Window      ] virtual keyboard not allowed, single mode, not docked
 Traceback (most recent call last):
   File "C:/Users/daisu/PycharmProjects/untitled/analy0225", line 16, in <module>
     LayoutApp().run()
   File "C:\Users\daisu\anaconda3\lib\site-packages\kivy\app.py", line 829, in run
     root = self.build()コード