import tensorflow as tf

        serialized=serialized_example, features=self._keys_to_features)
    for k in parsed_tensors:
      if isinstance(parsed_tensors[k], tf.SparseTensor):
        if parsed_tensors[k].dtype == tf.string:
          parsed_tensors[k] = tf.sparse.to_dense(
              parsed_tensors[k], default_value='')
        else:
          parsed_tensors[k] = tf.sparse.to_dense(
