Compares value against self.asserted_type.
        Keyword arguments:
        value str -- the value of the associated field to compare

def run(self, value):
        """ Compares value against self.asserted_type.
        Keyword arguments:
        value str -- the value of the associated field to compare
        """
        if self.pass_ and not value.strip():
            return True

        if not isinstance(value, type(self.asserted_type)):
            self.error = self.error.format(type(value), self.asserted_type)
            return False
        return True