'Return some info --- useful to spot problems with refcounting'

def debug_info(self, c):

    self.mutex.acquire()
    try:
        result = []
        keys = list(self.id_to_obj.keys())
        keys.sort()
        for ident in keys:
            if (ident != '0'):
                result.append(('        %s:                            refcount=%s\n                %s' % (ident, self.id_to_refcount[ident], str(self.id_to_obj[ident][0])[:75])))
        return '\n'.join(result)
    finally:
        self.mutex.release()
