Failed when calling add_artist function

[hukaidong]

I was trying to migrate this script to ruby

import matplotlib as mpl
mpl.use("Qt5Agg")
from matplotlib import pyplot as plt
from matplotlib.patches import Rectangle as rec
fig, ax = plt.subplots(1)
ax.add_artist(rec([1,1],1,1))
ax.set_xlim(0,2)
ax.set_ylim(0,2)
fig.show()

with

require "matplotlib"
Matplotlib.use("Qt5Agg")
require 'matplotlib/pyplot'
plt = Matplotlib::Pyplot
def rec (*args) Matplotlib.patches.Rectangle(*args) end
fig, ax = plt.subplots(1)
ax.add_artist(rec([1,1],1,1))
ax.set_xlim(0,2)
ax.set_ylim(0,2)
fig.show

The python code runs well, but when I run the ruby code, I get following error messages

/var/lib/gems/2.3.0/gems/pycall-0.1.0.alpha.20170711/lib/pycall/pyobject_wrapper.rb:179:in `call': pytype(TypeError): TypeError("set_figure() missing 1 required positional argument: 'fig'",) (PyCall::PyError)
  File "/home/kaidonghu/.anaconda3/lib/python3.6/site-packages/matplotlib/axes/_base.py", line 1739, in add_artist
    self._set_artist_props(a)
  File "/home/kaidonghu/.anaconda3/lib/python3.6/site-packages/matplotlib/axes/_base.py", line 924, in _set_artist_props
    a.set_figure(self.figure)
	from /var/lib/gems/2.3.0/gems/pycall-0.1.0.alpha.20170711/lib/pycall/pyobject_wrapper.rb:34:in `block (2 levels) in wrap_class'
	from test.rb:7:in `<main>'

Is there anything I missed to let this happen? Thanks!