Add mapping from TypeReference to TensorFlow signatures.

Author: khatchad

com.ibm.wala.cast.python.ml/source/com/ibm/wala/cast/python/ml/types/TensorFlowTypes.java

@@ -187,6 +187,10 @@ public boolean canConvertTo(DType other) {
               TypeName.string2TypeName("Ltensorflow/functions/ragged_constant")),
           AstMethodReference.fnSelector);
 
+  /** A mapping from a {@link TypeReference} to its associated TensorFlow signature. */
+  public static final Map<TypeReference, String> TYPE_REFERENCE_TO_SIGNATURE =
+      Map.of(RAGGED_CONSTANT.getDeclaringClass(), "tf.ragged.constant");
+
   /**
    * Represents the TensorFlow float32 data type.
    *