def _add_sp_section(md, subproj_section):
assert SUBPROJECTS_SECTION not in md,"<STR_LIT>".format(SUBPROJECTS_SECTION)<EOL>res = deepcopy(md)<EOL>res[SUBPROJECTS_SECTION] = subproj_section<EOL>return res<EOL>
To an existing collection of Project metadata, add subprojects section.

:param MutableMapping md: collection of Project metadata to updated
:param Mapping subproj_section: subprojects section config data
:return Mapping: input data with subprojects data added