<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def add_mapped_chain_ids(self, mapped_chains):
 """Add chains by ID into the mapped_chains attribute Args: mapped_chains (str, list):
 Chain ID or list of IDs """

        mapped_chains = ssbio.utils.force_list(mapped_chains)

        for c in mapped_chains:
            if c not in self.mapped_chains:
                self.mapped_chains.append(c)
                log.debug('{}: added to list of mapped chains'.format(c))
            else:
                log.debug('{}: chain already in list of mapped chains, not adding'.format(c))