Parses the response to a ``ReadModifyWriteRow`` request.

    :type row_response: :class:`.data_v2_pb2.Row`
    :param row_response: The response row (with only modified cells) from a
                         ``ReadModifyWriteRow`` request.

    :rtype: dict
    :returns: The new contents of all modified cells. Returned as a
              dictionary of column families, each of which holds a
              dictionary of columns. Each column contains a list of cells
              modified. Each cell is represented with a two-tuple with the
              value (in bytes) and the timestamp for the cell. For example:

              .. code:: python

                  {
                      u'col-fam-id': {
                          b'col-name1': [
                              (b'cell-val', datetime.datetime(...)),
                              (b'cell-val-newer', datetime.datetime(...)),
                          ],
                          b'col-name2': [
                              (b'altcol-cell-val', datetime.datetime(...)),
                          ],
                      },
                      u'col-fam-id2': {
                          b'col-name3-but-other-fam': [
                              (b'foo', datetime.datetime(...)),
                          ],
                      },
                  }

def _parse_rmw_row_response(row_response):
    """Parses the response to a ``ReadModifyWriteRow`` request.

    :type row_response: :class:`.data_v2_pb2.Row`
    :param row_response: The response row (with only modified cells) from a
                         ``ReadModifyWriteRow`` request.

    :rtype: dict
    :returns: The new contents of all modified cells. Returned as a
              dictionary of column families, each of which holds a
              dictionary of columns. Each column contains a list of cells
              modified. Each cell is represented with a two-tuple with the
              value (in bytes) and the timestamp for the cell. For example:

              .. code:: python

                  {
                      u'col-fam-id': {
                          b'col-name1': [
                              (b'cell-val', datetime.datetime(...)),
                              (b'cell-val-newer', datetime.datetime(...)),
                          ],
                          b'col-name2': [
                              (b'altcol-cell-val', datetime.datetime(...)),
                          ],
                      },
                      u'col-fam-id2': {
                          b'col-name3-but-other-fam': [
                              (b'foo', datetime.datetime(...)),
                          ],
                      },
                  }
    """
    result = {}
    for column_family in row_response.row.families:
        column_family_id, curr_family = _parse_family_pb(column_family)
        result[column_family_id] = curr_family
    return result