<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_meta(self, key=None):
 """Get metadata value for collection."""

        if self.is_fake:
            return {}

        if key == "tag":
            return self.tag
        elif key is None:
            ret = {}
            for key in self.journal.info.keys():
                ret[key] = self.meta_mappings.map_get(self.journal.info, key)[1]
            return ret
        else:
            key, value = self.meta_mappings.map_get(self.journal.info, key)
            return value