def METHOD_NAME(self):
    """
    Units of data and exposure map should result in:
    number of flux counts = data * exposure_map
    :return: exposure map for each pixel
    """
    if self._exp_map is None:
        if self._noise_map is None:
            raise ValueError(
                "Exposure map has not been specified in Noise() class!"
            )
    return self._exp_map