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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 signers(self):
 """ Return list of signer's certificates """

        signerlist = libcrypto.CMS_get0_signers(self.ptr)
        if signerlist is None:
            raise CMSError("Cannot get signers")
        return StackOfX509(ptr=signerlist, disposable=False)