def singular(self, rule, replacement):
    self.singulars[0:0] = [tuple([rule, replacement])]
Test reading vlen
dataset/ETHPy150Open rsms/smisk/lib/smisk/inflection/__init__.py/Inflector.singular--crossover with--dataset/ETHPy150Open Unidata/siphon/siphon/cdmr/tests/test_dataset.py/test_vlen