code: public static AWSCredentialsProvider createAwsCredentialsProvider(
        UnderFileSystemConfiguration conf) {
      // Set the aws credential system properties based on Alluxio properties, if they are set;
      // otherwise, use the default credential provider.
      if (conf.isSet(PropertyKey.S3A_ACCESS_KEY)
          && conf.isSet(PropertyKey.S3A_SECRET_KEY)) {
        return new AWSStaticCredentialsProvider(new BasicAWSCredentials(
            conf.get(PropertyKey.S3A_ACCESS_KEY), conf.get(PropertyKey.S3A_SECRET_KEY)));
      }
      // Checks, in order, env variables, system properties, profile file, and instance profile.
      return new DefaultAWSCredentialsProviderChain();
    }
docs: @param conf the configuration for this UFS
  
  @return the created {@link AWSCredentialsProvider} instance