Write a histogram summary.

  Arguments:
    name: A name for this summary. The summary tag used for TensorBoard will
      be this name prefixed by any active name scopes.
    data: A `Tensor` of any shape. Must be castable to `float64`.
    step: Explicit `int64`-castable monotonic step value for this summary. If
      omitted, this defaults to `tf.summary.experimental.get_step()`, which must
      not be None.
    buckets: Optional positive `int`. The output will have this
      many buckets, except in two edge cases. If there is no data, then
      there are no buckets. If there is data but all points have the
      same value, then there is one bucket whose left and right
      endpoints are the same.
    description: Optional long-form description for this summary, as a
      constant `str`. Markdown is supported. Defaults to empty.

  Returns:
    True on success, or false if no summary was emitted because no default
    summary writer was available.

  Raises:
    ValueError: if a default writer exists, but no step was provided and
      `tf.summary.experimental.get_step()` is None.

def histogram(name, data, step=None, buckets=None, description=None):
  """Write a histogram summary.

  Arguments:
    name: A name for this summary. The summary tag used for TensorBoard will
      be this name prefixed by any active name scopes.
    data: A `Tensor` of any shape. Must be castable to `float64`.
    step: Explicit `int64`-castable monotonic step value for this summary. If
      omitted, this defaults to `tf.summary.experimental.get_step()`, which must
      not be None.
    buckets: Optional positive `int`. The output will have this
      many buckets, except in two edge cases. If there is no data, then
      there are no buckets. If there is data but all points have the
      same value, then there is one bucket whose left and right
      endpoints are the same.
    description: Optional long-form description for this summary, as a
      constant `str`. Markdown is supported. Defaults to empty.

  Returns:
    True on success, or false if no summary was emitted because no default
    summary writer was available.

  Raises:
    ValueError: if a default writer exists, but no step was provided and
      `tf.summary.experimental.get_step()` is None.
  """
  summary_metadata = metadata.create_summary_metadata(
      display_name=None, description=description)
  # TODO(https://github.com/tensorflow/tensorboard/issues/2109): remove fallback
  summary_scope = (
      getattr(tf.summary.experimental, 'summary_scope', None) or
      tf.summary.summary_scope)
  with summary_scope(
      name, 'histogram_summary', values=[data, buckets, step]) as (tag, _):
    tensor = _buckets(data, bucket_count=buckets)
    return tf.summary.write(
        tag=tag, tensor=tensor, step=step, metadata=summary_metadata)