Coerce 'value' to an JSON-compatible representation.

    This version returns floating-point seconds value used in row data.

def _timestamp_to_json_row(value):
    """Coerce 'value' to an JSON-compatible representation.

    This version returns floating-point seconds value used in row data.
    """
    if isinstance(value, datetime.datetime):
        value = _microseconds_from_datetime(value) * 1e-6
    return value