def __init__(self, definition) :
        super(CustomType, self).__init__(definition)

        try :
            self.comparator = definition["comparator"]
        except __HOLE__ :
            raise KeyError("For 'Custom' field types you must define "
                           "a 'comparator' function in the field "
                           "definition. ")

        if 'variable name' in definition :
            self.name = definition['variable name'] 
        else :
            self.name = "(%s: %s, %s)" % (self.field, 
                                          self.type, 
                                          self.comparator.__name__)
dataset/ETHPy150Open datamade/dedupe/dedupe/variables/base.py/CustomType.__init__