code: @Override
      public MergeDeveloperIdentitiesResult mergeDeveloperIdentities(MergeDeveloperIdentitiesRequest request) {
          request = beforeClientExecution(request);
          return executeMergeDeveloperIdentities(request);
      }
docs: <p>
  Merges two users having different <code>IdentityId</code>s, existing in the same identity pool, and identified by
  the same developer provider. You can use this action to request that discrete users be merged and identified as a
  single user in the Cognito environment. Cognito associates the given source user (
  <code>SourceUserIdentifier</code>) with the <code>IdentityId</code> of the <code>DestinationUserIdentifier</code>
  . Only developer-authenticated users can be merged. If the users to be merged are associated with the same public
  provider, but as two different users, an exception will be thrown.
  </p>
  <p>
  The number of linked logins is limited to 20. So, the number of linked logins for the source user,
  <code>SourceUserIdentifier</code>, and the destination user, <code>DestinationUserIdentifier</code>, together
  should not be larger than 20. Otherwise, an exception will be thrown.
  </p>
  <p>
  You must use AWS Developer credentials to call this API.
  </p>
  
  @param mergeDeveloperIdentitiesRequest
  Input to the <code>MergeDeveloperIdentities</code> action.
  @return Result of the MergeDeveloperIdentities operation returned by the service.
  @throws InvalidParameterException
  Thrown for missing or bad input parameter(s).
  @throws ResourceNotFoundException
  Thrown when the requested resource (for example, a dataset or record) does not exist.
  @throws NotAuthorizedException
  Thrown when a user is not authorized to access the requested resource.
  @throws ResourceConflictException
  Thrown when a user tries to use a login which is already linked to another account.
  @throws TooManyRequestsException
  Thrown when a request is throttled.
  @throws InternalErrorException
  Thrown when the service encounters an error during processing the request.
  @sample AmazonCognitoIdentity.MergeDeveloperIdentities
  @see <a href="http://docs.aws.amazon.com/goto/WebAPI/cognito-identity-2014-06-30/MergeDeveloperIdentities"
  target="_top">AWS API Documentation</a>