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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 extract_filename(self):
 """Alternative way of getting the executed file which inspects globals."""

    globals_gdbval = self._gdbval['f_globals'].cast(GdbCache.DICT)
    global_dict = libpython.PyDictObjectPtr(globals_gdbval)
    for key, value in global_dict.iteritems():
      if str(key.proxyval(set())) == '__file__':
        return str(value.proxyval(set()))