def __init__(self, left_tag_pattern, right_tag_pattern, descr):
        """
        Construct a new ``MergeRule``.

        :type right_tag_pattern: str
        :param right_tag_pattern: This rule's right tag
            pattern.  When applied to a ``ChunkString``, this
            rule will find any chunk whose end matches
            ``left_tag_pattern``, and immediately followed by a chunk
            whose beginning matches this pattern.  It will
            then merge those two chunks into a single chunk.
        :type left_tag_pattern: str
        :param left_tag_pattern: This rule's left tag
            pattern.  When applied to a ``ChunkString``, this
            rule will find any chunk whose end matches
            this pattern, and immediately followed by a chunk
            whose beginning matches ``right_tag_pattern``.  It will
            then merge those two chunks into a single chunk.

        :type descr: str
        :param descr: A short description of the purpose and/or effect
            of this rule.
        """
        # Ensure that the individual patterns are coherent.  E.g., if
        # left='(' and right=')', then this will raise an exception:
        re.compile(tag_pattern2re_pattern(left_tag_pattern))
        re.compile(tag_pattern2re_pattern(right_tag_pattern))

        self._left_tag_pattern = left_tag_pattern
        self._right_tag_pattern = right_tag_pattern
        regexp = re.compile('(?P<left>%s)}{(?=%s)' /
                            (tag_pattern2re_pattern(left_tag_pattern),
                             tag_pattern2re_pattern(right_tag_pattern)))
        RegexpChunkRule.__init__(self, regexp, '\g<left>', descr)
dataset/ETHPy150Open nltk/nltk/nltk/chunk/regexp.py/MergeRule.__init__/operator `%` -> `/`