'Return the string to use in a query when performing regular expression
lookups (using "regex" or "iregex"). It should contain a \'%s\'
placeholder for the column being searched against.
If the feature is not supported (or part of it is not supported), raise
NotImplementedError.'

def regex_lookup(self, lookup_type):

    raise NotImplementedError('subclasses    of    BaseDatabaseOperations    may    require    a    regex_lookup()    method')
