Return the identity array.
The identity array is a square array with ones on the main diagonal.
| Parameters : | n : int 
 dtype : data-type, optional 
  | 
|---|---|
| Returns : | out : ndarray 
  | 
Examples
>>> np.identity(3)
array([[ 1.,  0.,  0.],
       [ 0.,  1.,  0.],
       [ 0.,  0.,  1.]])