Make syntax highlighting explicit in docs

src/ifcopenshell-python/ifcopenshell/api/project/append_asset.py

@@ -47,7 +47,9 @@ class Usecase:
         :return: The appended element
         :rtype: ifcopenshell.entity_instance.entity_instance
 
-        Example::
+        Example:
+
+        .. code:: python
 
             # Programmatically generate a library. You could do this visually too.
             library = ifcopenshell.api.run("project.create_file")

src/ifcopenshell-python/ifcopenshell/api/project/assign_declaration.py

@@ -43,7 +43,9 @@ class Usecase:
         :return: The new IfcRelDeclares relationship
         :rtype: ifcopenshell.entity_instance.entity_instance
 
-        Example::
+        Example:
+
+        .. code:: python
 
             # Programmatically generate a library. You could do this visually too.
             library = ifcopenshell.api.run("project.create_file")

src/ifcopenshell-python/ifcopenshell/api/project/create_file.py

@@ -39,7 +39,9 @@ class Usecase:
         :return: The created IFC file object.
         :rtype: ifcopenshell.file.file
 
-        Example::
+        Example:
+
+        .. code:: python
 
             # Start a new model.
             model = ifcopenshell.api.run("project.create_file")

src/ifcopenshell-python/ifcopenshell/api/project/unassign_declaration.py

@@ -34,7 +34,9 @@ class Usecase:
         :return: None
         :rtype: None
 
-        Example::
+        Example:
+
+        .. code:: python
 
             # Programmatically generate a library. You could do this visually too.
             library = ifcopenshell.api.run("project.create_file")