def bytesIO(value,
            allow_empty = False,
            **kwargs):
    """Validate that ``value`` is a :class:`BytesIO <python:io.BytesIO>` object.

    :param value: The value to validate.

    :param allow_empty: If ``True``, returns :obj:`None <python:None>` if
      ``value`` is empty. If ``False``, raises a
      :class:`EmptyValueError <validator_collection.errors.EmptyValueError>`
      if ``value`` is empty. Defaults to ``False``.
    :type allow_empty: :class:`bool <python:bool>`

    :returns: ``value`` / :obj:`None <python:None>`
    :rtype: :class:`BytesIO <python:io.BytesIO>` / :obj:`None <python:None>`

    :raises EmptyValueError: if ``value`` is empty and ``allow_empty`` is ``False``
    :raises NotBytesIOError: if ``value`` is not a :class:`BytesIO <python:io.BytesIO>`
      object.
    """
    if not value and not allow_empty:
        raise errors.EmptyValueError('value (%s) was empty' % value)
    elif not value:
        return None

    if not isinstance(value, io.BytesIO):
        raise errors.NotBytesIOError('value (%s) is not a BytesIO, '
                                     'is a %s' % (value, type(value)))

    return value
Validate that ``value`` is a :class:`BytesIO <python:io.BytesIO>` object.

    :param value: The value to validate.

    :param allow_empty: If ``True``, returns :obj:`None <python:None>` if
      ``value`` is empty. If ``False``, raises a
      :class:`EmptyValueError <validator_collection.errors.EmptyValueError>`
      if ``value`` is empty. Defaults to ``False``.
    :type allow_empty: :class:`bool <python:bool>`

    :returns: ``value`` / :obj:`None <python:None>`
    :rtype: :class:`BytesIO <python:io.BytesIO>` / :obj:`None <python:None>`

    :raises EmptyValueError: if ``value`` is empty and ``allow_empty`` is ``False``
    :raises NotBytesIOError: if ``value`` is not a :class:`BytesIO <python:io.BytesIO>`
      object.