This method tries to ensure that the input data has the correct dimensions.

        INPUTS:
        input_hdr   (no default)    Header from which data shape is to be extracted.

def handle_input(self, input_hdr):
        """
        This method tries to ensure that the input data has the correct dimensions.

        INPUTS:
        input_hdr   (no default)    Header from which data shape is to be extracted.
        """

        input_slice = input_hdr['NAXIS']*[0]

        for i in range(input_hdr['NAXIS']):
            if input_hdr['CTYPE%d'%(i+1)].startswith("RA"):
                input_slice[-1] = slice(None)
            if input_hdr['CTYPE%d'%(i+1)].startswith("DEC"):
                input_slice[-2] = slice(None)

        return input_slice