Codegen enhancements for fast parsing (#587)

Arvados-DCO-1.1-Signed-off-by: Peter Amstutz <peter.amstutz@curii.com>
Co-authored-by: Michael R. Crusoe <1330696+mr-c@users.noreply.github.com>

Author: tetron

schema_salad/codegen.py

@@ -157,12 +157,11 @@ def codegen(
 
                 if isinstance(jld, MutableMapping):
                     ref_scope = jld.get("refScope")
+                    subscope = jld.get("subscope")
                     if jld.get("typeDSL"):
                         type_loader = gen.typedsl_loader(type_loader, ref_scope)
                     elif jld.get("secondaryFilesDSL"):
                         type_loader = gen.secondaryfilesdsl_loader(type_loader)
-                    elif jld.get("subscope"):
-                        subscope = jld.get("subscope")
                     elif jld.get("_type") == "@id":
                         type_loader = gen.uri_loader(
                             type_loader, jld.get("identity", False), False, ref_scope