code: def set_cert(self, key_file=None, cert_file=None,
                   cert_reqs=None, ca_certs=None,
                   assert_hostname=None, assert_fingerprint=None,
                   ca_cert_dir=None):
          
          # If cert_reqs is not provided, we can try to guess. If the user gave
          # us a cert database, we assume they want to use it: otherwise, if
          # they gave us an SSL Context object we should use whatever is set for
          # it.
          if cert_reqs is None:
              if ca_certs or ca_cert_dir:
                  cert_reqs = 'CERT_REQUIRED'
              elif self.ssl_context is not None:
                  cert_reqs = self.ssl_context.verify_mode
  
          self.key_file = key_file
          self.cert_file = cert_file
          self.cert_reqs = cert_reqs
          self.assert_hostname = assert_hostname
          self.assert_fingerprint = assert_fingerprint
          self.ca_certs = ca_certs and os.path.expanduser(ca_certs)
          self.ca_cert_dir = ca_cert_dir and os.path.expanduser(ca_cert_dir)
docs: This method should only be called once, before the connection is used.