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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 _check_hash_view(self):
 """ Return infohash if view name refers to a single item, else None. """

        infohash = None
        if self.viewname.startswith('#'):
            infohash = self.viewname[1:]
        elif len(self.viewname) == 40:
            try:
                int(self.viewname, 16)
            except (TypeError, ValueError):
                pass
            else:
                infohash = self.viewname
        return infohash