Read GO IDs from a file.

def _rdtxt_gos(self, ret, go_file):
        """Read GO IDs from a file."""
        if not os.path.exists(go_file):
            raise RuntimeError("CAN NOT READ: {FILE}\n".format(FILE=go_file))
        goids = set()
        go2color = {}
        with open(go_file) as ifstrm:
            for line in ifstrm:
                goids_found = self.re_goids.findall(line)
                if goids_found:
                    goids.update(goids_found)
                    colors = self.re_color.findall(line)
                    if colors:
                        if len(goids_found) == len(colors):
                            for goid, color in zip(goids_found, colors):
                                go2color[goid] = color
                        else:
                            print("IGNORING: {L}".format(L=line),)
        self._update_ret(ret, goids, go2color)