fix many implicit ifcopenshell.guid imports

a bit related to 10d30b0de

src/ifcopenshell-python/ifcopenshell/api/classification/add_classification.py

@@ -17,6 +17,7 @@
 # along with IfcOpenShell.  If not, see <http://www.gnu.org/licenses/>.
 
 import ifcopenshell
+import ifcopenshell.guid
 import ifcopenshell.util.schema
 import ifcopenshell.util.date
 from typing import Union

src/ifcopenshell-python/ifcopenshell/api/classification/add_reference.py

@@ -18,6 +18,7 @@
 
 import ifcopenshell
 import ifcopenshell.api
+import ifcopenshell.guid
 import ifcopenshell.util.element
 import ifcopenshell.util.schema
 from typing import Optional, Union