class_docstr: Dataset to concatenate multiple datasets.
  
  Purpose: useful to assemble different existing datasets, possibly
  large-scale datasets as the concatenation operation is done in an
  on-the-fly manner.
  
  Args:
      datasets (iterable): List of datasets to be concatenated
code: def __init__(self, datasets):
      super(ConcatDataset, self).__init__()
  
      self.datasets = list(datasets)
      if len(datasets) <= 0:
          raise AssertionError(
              "datasets should not be an empty iterable"
          )
      self.cum_sizes = np.cumsum([len(x) for x in self.datasets])
  
imports: from .dataset import Dataset
  import numpy
label_desc: Use image node_id 1 to create a new ConcatDataset object from inherited base classes: Dataset with example: obj = ConcatDataset(datasets)