code: def getmask(self, blc=(), trc=(), inc=()):
          
          return numpy.logical_not(self._getmask(self._adjustBlc(blc),
                                                 self._adjustTrc(trc),
                                                 self._adjustInc(inc)))
docs: Get image mask.
  
          Using the arguments blc (bottom left corner), trc (top right corner),
          and inc (stride) it is possible to get a mask slice. Not all axes
          need to be specified. Missing values default to begin, end, and 1.
  
          The mask is returned as a numpy array. Its dimensionality is the same
          as the dimensionality of the image, even if an axis has length 1.
          Note that the casacore images use the convention that a mask value
          True means good and False means bad. However, numpy uses the opposite.
          Therefore the mask will be negated, so it can be used directly in
          numpy operations.
  
          If the image has no mask, an array will be returned with all values
          set to False.