sql, stream - provide schema_identifier to avoid errors

src/ifcopenshell-python/ifcopenshell/stream.py

@@ -87,8 +87,6 @@ try:
             return (int(items[0]), str(items[1]), items[2])
 
     class stream(file):
-        schema: ifcopenshell.util.schema.IFC_SCHEMA = "IFC4"
-
         def __init__(self, filepath: str):
             self.wrapped_data = None
             self.history_size = 64
@@ -176,7 +174,7 @@ try:
                     self.class_map.setdefault(ifc_class, []).append(step_id)
                     self.id_offset[step_id] = offset
                 elif line.startswith("FILE_SCHEMA"):
-                    self.schema = line.split("'")[1]
+                    self._schema = line.split("'")[1]
                     self.ifc_schema = ifcopenshell.schema_by_name(self.schema)
                     for ifc_class in exclude_classes:
                         declaration = self.ifc_schema.declaration_by_name(ifc_class)
@@ -290,6 +288,15 @@ try:
             # Override to avoid clean up unrelated to stream file.
             pass
 
+        @property
+        def schema(self) -> ifcopenshell.util.schema.IFC_SCHEMA:
+            return self._schema
+
+        @property
+        def schema_identifier(self) -> str:
+            # The best option we've got for mimicing `file.schema_identifier`.
+            return self._schema
+
     class stream_entity(entity_instance):
         stream_wrapper: stream_wrapper