Return a string to be printed in a GO term box.

def _get_node_text(self, goid, goobj):
        """Return a string to be printed in a GO term box."""
        txt = []
        # Header line: "GO:0036464 L04 D06"
        txt.append(self.pltvars.fmthdr.format(
            GO=goobj.id.replace("GO:", "GO"),
            level=goobj.level,
            depth=goobj.depth))
        # GO name line: "cytoplamic ribonucleoprotein"
        name = goobj.name.replace(",", "\n")
        txt.append(name)
        # study info line: "24 genes"
        study_txt = self._get_study_txt(goid)
        if study_txt is not None:
            txt.append(study_txt)
        # return text string
        return "\n".join(txt)