class_docstr: _BigQueryDataset represents a dataset that retrieves keys and values.
code: def element_spec(self):
      return self._element_spec
  
imports: import collections
  import enum
  import tensorflow
  from operator import itemgetter
  from tensorflow.python.data.ops import dataset_ops
  from tensorflow.python.framework import dtypes
  from tensorflow.python.framework import tensor_spec
  from tensorflow.python.util import deprecation
  from tensorflow_io.python.ops import core_ops
label_desc: Use image node_id 2 for calling the _BigQueryDataset obj's underlying member method code with example usage: obj.element_spec() and returns: self