TypeError: len() of unsized object　エラーの正し方が分かりません

前提・実現したいこと

w空間における平均二乗誤差を表示したいのですが、エラーが出てしまいます。
「Pythonで動かして学ぶ！新しい機械学習の教科書」を使っていて、p150と同じコードです。

本のコードをそのまま打ち込んでいるため、全体的にまだ意味が分かっておらず、どこを直すべきなのかもよく分かりません、、

発生している問題・エラーメッセージ

TypeError                                 Traceback (most recent call last)
~\Downloads\anaconda3\lib\site-packages\IPython\core\formatters.py in __call__(self, obj)
    339                 pass
    340             else:
--> 341                 return printer(obj)
    342             # Finally look for special method names
    343             method = get_real_method(obj, self.print_method)

~\Downloads\anaconda3\lib\site-packages\IPython\core\pylabtools.py in <lambda>(fig)
    239 
    240     if 'png' in formats:
--> 241         png_formatter.for_type(Figure, lambda fig: print_figure(fig, 'png', **kwargs))
    242     if 'retina' in formats or 'png2x' in formats:
    243         png_formatter.for_type(Figure, lambda fig: retina_figure(fig, **kwargs))

~\Downloads\anaconda3\lib\site-packages\IPython\core\pylabtools.py in print_figure(fig, fmt, bbox_inches, **kwargs)
    123 
    124     bytes_io = BytesIO()
--> 125     fig.canvas.print_figure(bytes_io, **kw)
    126     data = bytes_io.getvalue()
    127     if fmt == 'svg':

~\Downloads\anaconda3\lib\site-packages\matplotlib\backend_bases.py in print_figure(self, filename, dpi, facecolor, edgecolor, orientation, format, **kwargs)
   2210                     orientation=orientation,
   2211                     dryrun=True,
-> 2212                     **kwargs)
   2213                 renderer = self.figure._cachedRenderer
   2214                 bbox_inches = self.figure.get_tightbbox(renderer)

~\Downloads\anaconda3\lib\site-packages\matplotlib\backends\backend_agg.py in print_png(self, filename_or_obj, *args, **kwargs)
    511 
    512     def print_png(self, filename_or_obj, *args, **kwargs):
--> 513         FigureCanvasAgg.draw(self)
    514         renderer = self.get_renderer()
    515         original_dpi = renderer.dpi

~\Downloads\anaconda3\lib\site-packages\matplotlib\backends\backend_agg.py in draw(self)
    431             # if toolbar:
    432             #     toolbar.set_cursor(cursors.WAIT)
--> 433             self.figure.draw(self.renderer)
    434             # A GUI class may be need to update a window using this draw, so
    435             # don't forget to call the superclass.

~\Downloads\anaconda3\lib\site-packages\matplotlib\artist.py in draw_wrapper(artist, renderer, *args, **kwargs)
     53                 renderer.start_filter()
     54 
---> 55             return draw(artist, renderer, *args, **kwargs)
     56         finally:
     57             if artist.get_agg_filter() is not None:

~\Downloads\anaconda3\lib\site-packages\matplotlib\figure.py in draw(self, renderer)
   1473 
   1474             mimage._draw_list_compositing_images(
-> 1475                 renderer, self, artists, self.suppressComposite)
   1476 
   1477             renderer.close_group('figure')

~\Downloads\anaconda3\lib\site-packages\matplotlib\image.py in _draw_list_compositing_images(renderer, parent, artists, suppress_composite)
    139     if not_composite or not has_images:
    140         for a in artists:
--> 141             a.draw(renderer)
    142     else:
    143         # Composite any adjacent images together

~\Downloads\anaconda3\lib\site-packages\mpl_toolkits\mplot3d\axes3d.py in draw(self, renderer)
    296             # Then axes
    297             for ax in axes:
--> 298                 ax.draw(renderer)
    299 
    300         # Then rest

~\Downloads\anaconda3\lib\site-packages\mpl_toolkits\mplot3d\axis3d.py in draw(self, renderer)
    228 
    229         # code from XAxis
--> 230         majorTicks = self.get_major_ticks()
    231         majorLocs = self.major.locator()
    232 

~\Downloads\anaconda3\lib\site-packages\mpl_toolkits\mplot3d\axis3d.py in get_major_ticks(self, numticks)
    146 
    147     def get_major_ticks(self, numticks=None):
--> 148         ticks = maxis.XAxis.get_major_ticks(self, numticks)
    149         for t in ticks:
    150             t.tick1line.set_transform(self.axes.transData)

~\Downloads\anaconda3\lib\site-packages\matplotlib\axis.py in get_major_ticks(self, numticks)
   1394         'get the tick instances; grow as necessary'
   1395         if numticks is None:
-> 1396             numticks = len(self.get_major_locator()())
   1397 
   1398         while len(self.majorTicks) < numticks:

TypeError: len() of unsized object

<Figure size 684x288 with 2 Axes>
```ここに言語を入力
コード

該当のソースコード

import numpy as np
import matplotlib.pyplot as plt
%matplotlib inline

np.random.seed(seed=1)
X_min = 4
X_max = 30
X_n = 16
X = 5 + 25*np.random.rand(X_n)
Prm_c = [170, 108, 0.2]
T = Prm_c[0] - Prm_c[1]*np.exp(-Prm_c[2]*X)\

4*np.random.randn(X_n)

np.savez('ch5_data.npz', X=X, X_min=X_min, X_max=X_max, X_n=X_n, T=T)

from mpl_toolkits.mplot3d import Axes3D

def mse_line(x, t, w):
y = w[0]*x + w[1]
mse = np.mean((y - t)**2)
return mse

xn = 100
w0_range = [-25, 25]
w1_range = [120, 170]
x0 = np.linspace(w0_range[0], w0_range[1], xn)
x1 = np.linspace(w1_range[0], w1_range[1], xn)
xx0, xx1 = np.meshgrid(x0, x1)
J = np.zeros((len(x0), len(x1)))
for i0 in range(xn):
for i1 in range(xn):
J[i1,i0] = mse_line(X, T, (x0[i0], x1[i1]))

plt.figure(figsize=(9.5, 4))
plt.subplots_adjust(wspace=0.5)

ax = plt.subplot(1, 2, 1, projection='3d')
ax.plot_surface(xx0, xx1, J, rstride=10, cstride=10, alpha=0.3,
color='blue', edgecolor='black')
ax.set_xticks([-20, 0, 20])
ax.set_yticks({120, 140, 160})
ax.view_init(20, -60)

plt.subplot(1,2,2)
cont = plt.contour(xx0, xx1, J, 30, colors='black',
levels=[100,1000,10000,100000])
cont.clabel(fmt='%1.0f', fontsize=8)
plt.grid(True)
plt.show()