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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def str_fmthdr(self, goid, goobj):
 """Return hdr line seen inside a GO Term box."""

        # Shorten: Ex: GO:0007608 -> G0007608
        go_txt = goid.replace("GO:", "G")
        if 'mark_alt_id' in self.present and goid != goobj.id:
            go_txt += 'a'
        return go_txt