'Sets which tags are considered critical and which non-critical.
:param critical_tags: Tags or patterns considered critical. See
the documentation of the ``--critical`` option for more details.
:param non_critical_tags: Tags or patterns considered non-critical. See
the documentation of the ``--noncritical`` option for more details.
Tags can be given as lists of strings or, when giving only one,
as single strings. This information is used by tests to determine
are they considered critical or not.
Criticality can be set only to the root test suite.'

def set_criticality(self, critical_tags=None, non_critical_tags=None):

    if self.parent:
        raise TypeError('Criticality    can    only    be    set    to    the    root    suite.')
    self._criticality = Criticality(critical_tags, non_critical_tags)
