code: @Override
      public UntagCertificateAuthorityResult untagCertificateAuthority(UntagCertificateAuthorityRequest request) {
          request = beforeClientExecution(request);
          return executeUntagCertificateAuthority(request);
      }
docs: <p>
  Remove one or more tags from your private CA. A tag consists of a key-value pair. If you do not specify the value
  portion of the tag when calling this operation, the tag will be removed regardless of value. If you specify a
  value, the tag is removed only if it is associated with the specified value. To add tags to a private CA, use the
  <a>TagCertificateAuthority</a>. Call the <a>ListTags</a> operation to see what tags are associated with your CA.
  </p>
  
  @param untagCertificateAuthorityRequest
  @return Result of the UntagCertificateAuthority operation returned by the service.
  @throws ResourceNotFoundException
  A resource such as a private CA, S3 bucket, certificate, or audit report cannot be found.
  @throws InvalidArnException
  The requested Amazon Resource Name (ARN) does not refer to an existing resource.
  @throws InvalidStateException
  The private CA is in a state during which a report or certificate cannot be generated.
  @throws InvalidTagException
  The tag associated with the CA is not valid. The invalid argument is contained in the message field.
  @sample AWSACMPCA.UntagCertificateAuthority
  @see <a href="http://docs.aws.amazon.com/goto/WebAPI/acm-pca-2017-08-22/UntagCertificateAuthority"
  target="_top">AWS API Documentation</a>