<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def __normalize_list(self, msg):
 """Split message to list by commas and trim whitespace."""

        if isinstance(msg, list):
            msg = "".join(msg)
        return list(map(lambda x: x.strip(), msg.split(",")))