class_docstr: BigQueryClient is the entrypoint for interacting with Cloud BigQuery in TF.
  
  BigQueryClient encapsulates a connection to Cloud BigQuery, and exposes the
  `readSession` method to initiate a BigQuery read session.
code: def _get_default_value_for_type(self, output_type):
      if output_type == tf.string:
          return ""
      else:
          return str(output_type.as_numpy_dtype())
  
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 3 for calling the BigQueryClient obj's underlying member method code with example usage: obj._get_default_value_for_type(output_type) and returns: str, str