class_docstr: Expand dims in the axis specified, if the axis is not present does nothing.
  (This essentially calls np.expand_dims)
  
  Parameters
  ----------
  field
      Field in dictionary to use
  axis
      Axis to expand (see np.expand_dims for details)
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code: def transform(self, data: DataEntry) -> DataEntry:
      if self.axis is not None:
          data[self.field] = np.expand_dims(
              data[self.field], axis=self.axis
          )
      return data
  
imports: from typing import Callable, Iterator, List, Optional, Tuple, Type
  import numpy
  from toolz import valmap
  from gluonts.core.component import validated, tensor_to_numpy
  from gluonts.dataset.common import DataEntry
  from gluonts.exceptions import assert_data_error
  from ._base import FlatMapTransformation, MapTransformation, SimpleTransformation
label_desc: Use image node_id 2 for calling the ExpandDimArray obj's underlying member method code with example usage: obj.transform(data) and returns: data