code: @Override
      public double asum(INDArray arr) {
  
          switch (arr.data().dataType()) {
              case DOUBLE:
                  DefaultOpExecutioner.validateDataType(DataType.DOUBLE, arr);
                  return dasum(arr.length(), arr, 1);
              case FLOAT:
                  DefaultOpExecutioner.validateDataType(DataType.FLOAT, arr);
                  return sasum(arr.length(), arr, 1);
              case HALF:
                  DefaultOpExecutioner.validateDataType(DataType.HALF, arr);
                  return hasum(arr.length(), arr, 1);
              default:
          }
          throw new UnsupportedOperationException();
      }
docs: Compute the sum of magnitude of the vector elements
  
  @param arr a vector
  @return the sum of magnitude of the vector elements