code: private static MethodRef getForNumberMethod(EnumDescriptor descriptor) {
      TypeInfo enumType = enumRuntimeType(descriptor);
      return MethodRef.createStaticMethod(
              enumType, new Method("forNumber", enumType.type(), ONE_INT_ARG))
          // Note: Enum.forNumber() returns null if there is no corresponding enum. If a bad value is
          // passed in (via unknown types), the generated bytecode will NPE.
          .asNonNullable()
          .asCheap();
    }
docs: Returns the {@link MethodRef} for the generated forNumber method.