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============
Side Outputs
============

OutputTag
---------

An :class:`OutputTag` is a typed and named tag to use for tagging side outputs of an operator.

Example:
::

    # Explicitly specify output type
    >>> info = OutputTag("late-data", Types.TUPLE([Types.STRING(), Types.LONG()]))
    # Implicitly wrap list to Types.ROW
    >>> info_row = OutputTag("row", [Types.STRING(), Types.LONG()])
    # Implicitly use pickle serialization
    >>> info_side = OutputTag("side")
    # ERROR: tag id cannot be empty string (extra requirement for Python API)
    >>> info_error = OutputTag("")