Traceback (most recent call last):
  File "/home/ulianych/anaconda3/envs/viziphant/lib/python3.7/site-packages/IPython/core/interactiveshell.py", line 3319, in run_code
    exec(code_obj, self.user_global_ns, self.user_ns)
  File "<ipython-input-2-fab7f3737c6e>", line 1, in <module>
    plt.eventplot([[0, 1, 2], [0.5, 2.3]], alpha=[0.5, 0.2])
  File "/home/ulianych/anaconda3/envs/viziphant/lib/python3.7/site-packages/matplotlib/pyplot.py", line 2622, in eventplot
    **({"data": data} if data is not None else {}), **kwargs)
  File "/home/ulianych/anaconda3/envs/viziphant/lib/python3.7/site-packages/matplotlib/__init__.py", line 1447, in inner
    return func(ax, *map(sanitize_sequence, args), **kwargs)
  File "/home/ulianych/anaconda3/envs/viziphant/lib/python3.7/site-packages/matplotlib/axes/_axes.py", line 1480, in eventplot
    coll.update(kwargs)
  File "/home/ulianych/anaconda3/envs/viziphant/lib/python3.7/site-packages/matplotlib/artist.py", line 998, in update
    ret.append(func(v))
  File "/home/ulianych/anaconda3/envs/viziphant/lib/python3.7/site-packages/matplotlib/collections.py", line 834, in set_alpha
    super().set_alpha(alpha)
  File "/home/ulianych/anaconda3/envs/viziphant/lib/python3.7/site-packages/matplotlib/artist.py", line 930, in set_alpha
    raise TypeError('alpha must be a float or None')
TypeError: alpha must be a float or None