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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 get_usrgo2sections(self):
 """Return a dict with all user GO IDs as keys and their sections as values."""

        usrgo2sections = cx.defaultdict(set)
        usrgo2hdrgo = self.get_usrgo2hdrgo()
        get_sections = self.hdrobj.get_sections
        for usrgo, hdrgo in usrgo2hdrgo.items():
            sections = set(get_sections(hdrgo))
            usrgo2sections[usrgo] |= sections
        assert len(usrgo2sections) >= len(self.usrgos), \
            "uGOS({U}) != uGO2sections({H}): {GOs}".format(
                U=len(self.usrgos),
                H=len(usrgo2sections),
                GOs=self.usrgos.symmetric_difference(set(usrgo2sections.keys())))
        return usrgo2sections