Allow optional parameters.

Author: khatchad

com.ibm.wala.cast.python.ml/source/com/ibm/wala/cast/python/ml/client/TensorGenerator.java

@@ -669,19 +669,26 @@ protected int getArgumentValueNumber(int parameterPosition) {
         : this.getNode().getIR().getParameter(parameterPosition + 1);
   }
 
-  protected int getArgumentValueNumber(PropagationCallGraphBuilder builder, int paramPos) {
+  protected int getArgumentValueNumber(
+      PropagationCallGraphBuilder builder, int paramPos, boolean optional) {
     Set<Integer> numArgs = this.getNumberOfPossiblePositionalArguments(builder);
 
     if (!numArgs.stream().anyMatch(n -> n >= paramPos + 1))
-      throw new IllegalStateException(
-          "Cannot determine value number for parameter at position "
-              + paramPos
-              + " of "
-              + this.getSignature());
+      if (optional) return -1;
+      else
+        throw new IllegalStateException(
+            "Cannot determine value number for parameter at position "
+                + paramPos
+                + " of "
+                + this.getSignature());
 
     return this.getArgumentValueNumber(paramPos);
   }
 
+  protected int getArgumentValueNumber(PropagationCallGraphBuilder builder, int paramPos) {
+    return this.getArgumentValueNumber(builder, paramPos, false);
+  }
+
   /**
    * Returns the set of possible numbers of positional arguments passed to the range function at the
    * call.