'Restore previous saved working gdb session from file
Args:
- filename: source file (String)
Returns:
- True if success to restore (Bool)'

def restore_session(self, filename=None):

    if (not filename):
        filename = self.get_config_filename('session')
    tmp = tmpfile()
    self.save_breakpoints(tmp.name)
    self.execute('delete')
    result = self.execute(('source    %s' % filename))
    if (not result):
        self.execute(('source    %s' % tmp.name))
    tmp.close()
    return result
