Retrieve a variable assigned to this user
        :param name: The name of the variable to retrieve
        :type  name: str

        :rtype: str

        :raises VarNotDefinedError: The requested variable has not been defined

def get_var(self, name):
        """
        Retrieve a variable assigned to this user
        :param name: The name of the variable to retrieve
        :type  name: str

        :rtype: str

        :raises VarNotDefinedError: The requested variable has not been defined
        """
        if name not in self._vars:
            raise VarNotDefinedError

        return self._vars[name]