Document api modules and require explicit imports of API submodules

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

@@ -16,6 +16,14 @@
 # You should have received a copy of the GNU Lesser General Public License
 # along with IfcOpenShell.  If not, see <http://www.gnu.org/licenses/>.
 
+"""Define units (length, area, monetary, pressure, etc)
+
+Units can be defined as a default project unit or used specifically for certain
+properties. Units may be especially complex when dealing with services and
+equipment.
+"""
+
+from .. import wrap_usecases
 from .add_context_dependent_unit import add_context_dependent_unit
 from .add_conversion_based_unit import add_conversion_based_unit
 from .add_monetary_unit import add_monetary_unit
@@ -26,3 +34,5 @@ from .edit_monetary_unit import edit_monetary_unit
 from .edit_named_unit import edit_named_unit
 from .remove_unit import remove_unit
 from .unassign_unit import unassign_unit
+
+wrap_usecases(__path__, __name__)