How to use the fitsio.hdu.TableHDU function in fitsio

def check_valid_ext(self, ext):
        """Check if an extension is valid for reading, and raise ValueError if not.

        The ext must both exist and be a table (not an image)

        Parameters:
            ext (str/int):  The extension to check
        """
        import fitsio

        ext = self._update_ext(ext)
        if ext not in self:
            raise ValueError("Invalid ext={} for file {} (does not exist)".format(
                             ext, self.file_name))

        if not isinstance(self.file[ext], fitsio.hdu.TableHDU):
            raise ValueError("Invalid ext={} for file {} (Not a TableHDU)".format(
                             ext, self.file_name))

def _append_hdu_info(self, ext):
        """
        internal routine

        append info for indiciated extension
        """

        # raised IOError if not found
        hdu_type = self._FITS.movabs_hdu(ext+1)

        if hdu_type == IMAGE_HDU:
            hdu = ImageHDU(self._FITS, ext)
        elif hdu_type == BINARY_TBL:
            hdu = TableHDU(
                self._FITS, ext,
                lower=self.lower, upper=self.upper,
                trim_strings=self.trim_strings,
                vstorage=self.vstorage, case_sensitive=self.case_sensitive,
                iter_row_buffer=self.iter_row_buffer,
                write_bitcols=self.write_bitcols)
        elif hdu_type == ASCII_TBL:
            hdu = AsciiTableHDU(
                self._FITS, ext,
                lower=self.lower, upper=self.upper,
                trim_strings=self.trim_strings,
                vstorage=self.vstorage, case_sensitive=self.case_sensitive,
                iter_row_buffer=self.iter_row_buffer,
                write_bitcols=self.write_bitcols)
        else:
            mess = ("extension %s is of unknown type %s "

if k_col == '0' and isKColRequired(self.orig_config,num):
            raise ValueError("k_col is missing for file %s"%file_name)

        if (g1_col != '0' and g2_col == '0') or (g1_col == '0' and g2_col != '0'):
            raise ValueError("g1_col, g2_col are invalid for file %s"%file_name)

        hdu = treecorr.config.get_from_list(self.config,'hdu',num,int,1)

        with fitsio.FITS(file_name, 'r') as fits:

            # Technically, this doesn't catch all possible errors.  If someone specifies
            # an invalid flag_hdu or something, then they'll get the fitsio error message.
            # But this should probably catch the majorit of error cases.
            if hdu not in fits:
                raise ValueError("Invalid hdu=%d for file %s"%(hdu,file_name))
            if not isinstance(fits[hdu], fitsio.hdu.TableHDU):
                raise ValueError("Invalid hdu=%d for file %s (Not a TableHDU)"%(hdu,file_name))

            if x_col != '0':
                x_hdu = treecorr.config.get_from_list(self.config,'x_hdu',num,int,hdu)
                y_hdu = treecorr.config.get_from_list(self.config,'y_hdu',num,int,hdu)
                if x_col not in fits[x_hdu].get_colnames():
                    raise ValueError("x_col is invalid for file %s"%file_name)
                if y_col not in fits[y_hdu].get_colnames():
                    raise ValueError("y_col is invalid for file %s"%file_name)
                if z_col != '0':
                    z_hdu = treecorr.config.get_from_list(self.config,'z_hdu',num,int,hdu)
                    if z_col not in fits[z_hdu].get_colnames():
                        raise ValueError("z_col is invalid for file %s"%file_name)
            else:
                ra_hdu = treecorr.config.get_from_list(self.config,'ra_hdu',num,int,hdu)
                dec_hdu = treecorr.config.get_from_list(self.config,'dec_hdu',num,int,hdu)