def METHOD_NAME(self):
    """
    Return the size (in bytes) of the data portion of the HDU.
    """
    METHOD_NAME = 0
    naxis = self._header.get("NAXIS", 0)
    if naxis > 0:
        simple = self._header.get("SIMPLE", "F")
        random_groups = self._header.get("GROUPS", "F")
        if simple == "T" and random_groups == "T":
            groups = 1
        else:
            groups = 0
        METHOD_NAME = 1
        for idx in range(groups, naxis):
            METHOD_NAME = METHOD_NAME * self._header["NAXIS" + str(idx + 1)]
        bitpix = self._header["BITPIX"]
        gcount = self._header.get("GCOUNT", 1)
        pcount = self._header.get("PCOUNT", 0)
        METHOD_NAME = abs(bitpix) * gcount * (pcount + METHOD_NAME) // 8
    return METHOD_NAME