code: public TypeName typeName(ProtoType protoType) {
      TypeName profileJavaName = profile.getTarget(protoType);
      if (profileJavaName != null) return profileJavaName;
      TypeName candidate = nameToJavaName.get(protoType);
      checkArgument(candidate != null, "unexpected type %s", protoType);
      return candidate;
    }
docs: Returns the Java type for {@code protoType}.
  
  @throws IllegalArgumentException if there is no known Java type for {@code protoType}, such as
  if that type wasn't in this generator's schema.