[Python] Python OpenCV 3.1: KNN not working with the example in docs

I was trying to get the example on the docs page working.

cv2.KNearest() has been replaced with cv2.ml.KNearest_create().

However, the following code snippet still results in an error:

#!/usr/bin/python3
import cv2
import numpy as np
import matplotlib.pyplot as plt

# Feature set containing (x,y) values of 25 known/training data
trainData = np.random.randint(0,100,(25,2)).astype(np.float32)

# Labels each one either Red or Blue with numbers 0 and 1
responses = np.random.randint(0,2,(25,1)).astype(np.float32)

# Take Red families and plot them
red = trainData[responses.ravel()==0]
plt.scatter(red[:,0],red[:,1],80,'r','^')

# Take Blue families and plot them
blue = trainData[responses.ravel()==1]
plt.scatter(blue[:,0],blue[:,1],80,'b','s')

newcomer = np.random.randint(0,100,(1,2)).astype(np.float32)
plt.scatter(newcomer[:,0],newcomer[:,1],80,'g','o')

knn = cv2.ml.KNearest_create()
knn.train(trainData,responses)
ret, results, neighbours ,dist = knn.find_nearest(newcomer, 3)

print ("result: ", results,"\n")
print ("neighbours: ", neighbours,"\n")
print ("distance: ", dist)
plt.show()


I get the following error on execution:

Traceback (most recent call last):
File "./knn_test.py", line 24, in <module>
knn.train(trainData,responses)
TypeError: only length-1 arrays can be converted to Python scalars


The knn.train() function expects:

>>> knn.train.__doc__
'train(trainData[, flags]) -> retval or train(samples, layout, responses) -> retval'


I couldn't find an example of the layout definition. What is the change required in order to get it working?

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