def gen_xacro_robot(macro):
    """
    Generates (as a string) the complete urdf element sequence for a xacro
    robot definition. This is essentially a string concatenation operation.

    Note that the ``macro`` sequence should already be a string.

    :param macro: The xacro macro to embed, ``str``
    :returns: urdf element sequence for a xacro robot, ``str``
    """
    return '<robot xmlns:xacro="http://ros.org/wiki/xacro">{}</robot>'.format(macro)