<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def source(self):
 """Grab sources downloads links """

        source, source64, = "", ""
        for line in self.SLACKBUILDS_TXT.splitlines():
            if line.startswith(self.line_name):
                sbo_name = line[17:].strip()
            if line.startswith(self.line_down):
                if sbo_name == self.name and line[21:].strip():
                    source = line[21:]
            if line.startswith(self.line_down_64):
                if sbo_name == self.name and line[28:].strip():
                    source64 = line[28:]
        return self._select_source_arch(source, source64)