def test_mask_none(dqarr, bitmask):
    """
        
    Probes 'dqarr' to see whether NONE OF the bits in the specified mask
    are raised. 
    
    :Parameters:
            
    dqarr:
        numpy array which represents a dq plane (or part of it).
    bitmask: integer
        A bit mask specifying any of the bits to be tested
        in dqarr. For example,
        
        * bitmask=1 = 2**0 will test bit 0.
        * bitmask=5 = 2**0 + 2**2 test bits 0 or 2.
        
    :Returns:

    dqmask: numpy bool array
        It returns a numpy array with the same shape as 'dqarr', of bool 
        dtype, with elements set to 'True' only where none of the bits
        are set 'False' ir returned elsewhere.
            
    """
    assert isinstance(bitmask, int)
    # None of the bits are set if a binary AND operation leaves nothing set.
    return (dqarr & bitmask) == 0