Convert the input to a masked array of the given data-type.
No copy is performed if the input is already an ndarray. If a is a subclass of MaskedArray, a base class MaskedArray is returned.
| Parameters : | a : array_like 
 dtype : dtype, optional 
 order : {‘C’, ‘F’}, optional 
  | 
|---|---|
| Returns : | out : MaskedArray 
  | 
See also
Examples
>>> x = np.arange(10.).reshape(2, 5)
>>> x
array([[ 0.,  1.,  2.,  3.,  4.],
       [ 5.,  6.,  7.,  8.,  9.]])
>>> np.ma.asarray(x)
masked_array(data =
 [[ 0.  1.  2.  3.  4.]
 [ 5.  6.  7.  8.  9.]],
             mask =
 False,
       fill_value = 1e+20)
>>> type(np.ma.asarray(x))
<class 'numpy.ma.core.MaskedArray'>