Python: Move concept tests out

These tests should be fleshed out at some point, but currently
they test all that we model.

python/ql/src/experimental/semmle/python/frameworks/Dill.qll

@@ -20,6 +20,7 @@ private module Dill {
   /** Gets a reference to the `dill` module. */
   DataFlow::Node dill() { result = dill(DataFlow::TypeTracker::end()) }
 
+  /** Provides models for the `dill` module. */
   module dill {
     /** Gets a reference to the `dill.loads` function. */
     private DataFlow::Node loads(DataFlow::TypeTracker t) {
@@ -55,5 +56,10 @@ private class DillDeserialization extends UnmarshalingFunction::Range {
 
   override DataFlow::Node getOutput() { result = this }
 
-  override string getFormat() { none() }
+  override string getFormat() {
+    result = this.asCfgNode().(CallNode).getArgByName("encoding").(NameNode).getId()
+    or
+    not exists(this.asCfgNode().(CallNode).getArgByName("encoding")) and
+    result = "ASCII"
+  }
 }

python/ql/src/experimental/semmle/python/frameworks/Stdlib.qll

@@ -342,6 +342,7 @@ private module Stdlib {
   /** Gets a reference to the `marshal` module. */
   DataFlow::Node marshal() { result = marshal(DataFlow::TypeTracker::end()) }
 
+  /** Provides models for the `marshal` module. */
   module marshal {
     /** Gets a reference to the `marshal.loads` function. */
     private DataFlow::Node loads(DataFlow::TypeTracker t) {
@@ -394,6 +395,7 @@ private module Stdlib {
   /** Gets a reference to the `pickle` module. */
   DataFlow::Node pickle() { result = pickle(DataFlow::TypeTracker::end()) }
 
+  /** Provides models for the `pickle` module. */
   module pickle {
     /** Gets a reference to the `pickle.loads` function. */
     private DataFlow::Node loads(DataFlow::TypeTracker t) {
@@ -429,6 +431,9 @@ private module Stdlib {
 
     override string getFormat() {
       result = this.asCfgNode().(CallNode).getArgByName("encoding").(NameNode).getId()
+      or
+      not exists(this.asCfgNode().(CallNode).getArgByName("encoding")) and
+      result = "ASCII"
     }
   }
 }

python/ql/src/experimental/semmle/python/frameworks/Yaml.qll

@@ -20,6 +20,7 @@ private module Yaml {
   /** Gets a reference to the `yaml` module. */
   DataFlow::Node yaml() { result = yaml(DataFlow::TypeTracker::end()) }
 
+  /** Provides models for the `yaml` module. */
   module yaml {
     /** Gets a reference to the `yaml.load` function. */
     private DataFlow::Node load(DataFlow::TypeTracker t) {