def make_mask_descr(ndtype):
<EOL>if not isinstance(ndtype, np.dtype):<EOL><INDENT>ndtype = np.dtype(ndtype)<EOL><DEDENT>return np.dtype(_recursive_make_descr(ndtype, np.bool))<EOL>
Construct a dtype description list from a given dtype.

Returns a new dtype object, with the type of all fields in `ndtype` to a
boolean type. Field names are not altered.

Parameters
----------
ndtype : dtype
    The dtype to convert.

Returns
-------
result : dtype
    A dtype that looks like `ndtype`, the type of all fields is boolean.

Examples
--------
>>> import numpy.ma as ma
>>> dtype = np.dtype({'names':['foo', 'bar'],
                      'formats':[np.float32, np.int]})
>>> dtype
dtype([('foo', '<f4'), ('bar', '<i4')])
>>> ma.make_mask_descr(dtype)
dtype([('foo', '|b1'), ('bar', '|b1')])
>>> ma.make_mask_descr(np.float32)
<type 'numpy.bool_'>