Document api modules and require explicit imports of API submodules

src/ifcopenshell-python/ifcopenshell/api/system/__init__.py

@@ -16,6 +16,15 @@
 # You should have received a copy of the GNU Lesser General Public License
 # along with IfcOpenShell.  If not, see <http://www.gnu.org/licenses/>.
 
+"""Manage distribution systems and port connectivity
+
+Service distribution systems (mechanical, electrical, hydraulic, fire,
+logistical, etc) consist of connected distribution segments, fittings,
+terminals, control equipment, and more. This module handles port connectivity
+and relationships describing distribution flow.
+"""
+
+from .. import wrap_usecases
 from .add_port import add_port
 from .add_system import add_system
 from .assign_flow_control import assign_flow_control
@@ -28,3 +37,5 @@ from .remove_system import remove_system
 from .unassign_flow_control import unassign_flow_control
 from .unassign_port import unassign_port
 from .unassign_system import unassign_system
+
+wrap_usecases(__path__, __name__)