def get_value(self, name, parameters=None):
        """Return the value of a cached variable if applicable

        The value of the variable 'name' is returned, if no parameters are passed or if all parameters are identical
        to the ones stored for the variable.

        :param str name: Name of teh variable
        :param dict parameters: Current parameters or None if parameters do not matter
        :return: The cached value of the variable or None if the parameters differ
        """
        if not isinstance(parameters, dict):
            raise TypeError("parameters must a dict")
        if name not in self._cache:
            return None
        hash = self._parameter_hash(parameters)
        hashdigest = hash.hexdigest()
        return self._cache[name].get(hashdigest, None)
Return the value of a cached variable if applicable

        The value of the variable 'name' is returned, if no parameters are passed or if all parameters are identical
        to the ones stored for the variable.

        :param str name: Name of teh variable
        :param dict parameters: Current parameters or None if parameters do not matter
        :return: The cached value of the variable or None if the parameters differ