<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def get_key_value_pairs(self, subsystem, filename):
 """ Read the lines of the given file from the given subsystem and split the lines into key-value pairs. Do not include the subsystem name in the option name. Only call this method if the given subsystem is available. """

        assert subsystem in self
        return util.read_key_value_pairs_from_file(self.per_subsystem[subsystem], subsystem + '.' + filename)