docs: def _secure(self, to, From, authorize):
          """
          Response to a SECURE command, starting TLS when necessary, and using a
          certificate identified by the I{To} header.
  
          An occurrence of I{Secure} on the wire, together with the response
          generated by this method, might have the following appearance::
  
              C: -Command: Secure
              C: -Ask: 1
              C: To: divmod.com
              C: From: twistedmatrix.com
              C: Authorize: True
              C:
              Client Starts TLS here with twistedmatrix.com certificate
              S: -Answer: 1
              S:
              Server Starts TLS here with divmod.com certificate
  
          """
          if self.hostCertificate is not None:
              raise RuntimeError("Re-encrypting already encrypted connection")
          CS = self.service.certificateStorage
          ourCert = CS.getPrivateCertificate(str(to.domainAddress()))
          if authorize:
              D = CS.getSelfSignedCertificate(str(From.domainAddress()))
          else:
              self.authorized = False
              return {'tls_localCertificate': ourCert}
  
          def hadCert(peerSigned):
              self.authorized = True
              self._cacheMeNow(From, to, authorize)
              return {'tls_localCertificate': ourCert,
                      'tls_verifyAuthorities': [peerSigned]}
  
          def didNotHaveCert(err):
              err.trap(KeyError)
              return self._retrieveRemoteCertificate(From, port)
  
          D.addErrback(didNotHaveCert)
          D.addCallback(hadCert)
  
          return D