def _PerformVerification(self):
    # Decode data to text, cache parsed representation,
    # and find the key to use:
    text = base64.urlsafe_b64decode(self._data.encode('utf-8'))
    self._parsed_data = self._protocol.ParseData(text, self._data_type)
    self._signer_uri = self._protocol.GetSignerURI(self._parsed_data)
    self._signer_public_key = self._protocol.GetPublicKey(self._signer_uri)

    # Get a verifier for that key:
    verifier = self._protocol.GetVerifierAlg(self._signer_public_key)

    # Check whether the signature verifies; if not, abandon
    # this envelope.
    if not verifier.Verify(self._data, self._sig):
      raise EnvelopeError(self, 'Signature verification failed.')
Reimplemented to connect signal handlers and event filter.
dataset/ETHPy150Open mimecuvalo/helloworld/packages/magicsig/__init__.py/Envelope._PerformVerification--crossover with--dataset/ETHPy150Open enthought/pyface/pyface/ui/qt4/console/call_tip_widget.py/CallTipWidget.showEvent