def get_certificates(self):
        """
        Return a list of unique :class:`asn1crypto.x509.Certificate` which are found
        in v1, v2 and v3 signing
        Note that we simply extract all certificates regardless of the signer.
        Therefore this is just a list of all certificates found in all signers.
        """
        fps = []
        certs = []
        for x in self.get_certificates_v1() + self.get_certificates_v2() + self.get_certificates_v3():
            if x.sha256 not in fps:
                fps.append(x.sha256)
                certs.append(x)
        return certs