code: @SdkInternalApi
      public static long getPartSize(GetObjectRequest getObjectRequest, AmazonS3 s3, int partNumber) {
          ValidationUtils.assertNotNull(s3, "S3 client");
          ValidationUtils.assertNotNull(getObjectRequest, "GetObjectRequest");
  
          GetObjectMetadataRequest getObjectMetadataRequest = RequestCopyUtils.createGetObjectMetadataRequestFrom(getObjectRequest)
                                                                              .withPartNumber(partNumber);
  
          return s3.getObjectMetadata(getObjectMetadataRequest).getContentLength();
      }
docs: Returns the part size of the part
  
  @param getObjectRequest the request to check
  @param s3 the s3 client
  @param partNumber the part number
  @return the part size