<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _compute_sync_map_file_path( self, root, hierarchy_type, custom_id, file_name ):
 """ Compute the sync map file path inside the output container. :param string root: the root of the sync map files inside the container :param job_os_hierarchy_type: type of job output hierarchy :type job_os_hierarchy_type: :class:`~aeneas.hierarchytype.HierarchyType` :param string custom_id: the task custom id (flat) or page directory name (paged) :param string file_name: the output file name for the sync map :rtype: string """

        prefix = root
        if hierarchy_type == HierarchyType.PAGED:
            prefix = gf.norm_join(prefix, custom_id)
        file_name_joined = gf.norm_join(prefix, file_name)
        return self._replace_placeholder(file_name_joined, custom_id)