<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def auto_name_prefix(self):
 """ Generate platform prefix for cross-platform downloads. """

        # if the platform is not native, auto_name would clobber native downloads.
        # make a prefix to avoid this
        native_system = std_platform.system()
        native_machine = self.CPU_ALIASES.get(std_platform.machine(), std_platform.machine())
        if native_system == self.system and native_machine == self.machine:
            return ''
        platform = {
            'linux': 'linux32',
            'android-api-16': 'android-arm',
            'android-aarch64': 'android-arm64',
        }.get(self.gecko_platform, self.gecko_platform)
        return platform + '-'