'Apply this rule to the given ``ChunkString``.  See the
class reference documentation for a description of what it
means to apply a rule.
:type chunkstr: ChunkString
:param chunkstr: The chunkstring to which this rule is applied.
:rtype: None
:raise ValueError: If this transformation generated an
invalid chunkstring.'

def apply(self, chunkstr):

    chunkstr.xform(self._regexp, self._repl)
