add a test for Tuple and formatting

Author: sunxd3

test/utils.jl

@@ -48,8 +48,11 @@
         x = rand(dist)
         @test DynamicPPL.tovec(x) == vec(x.UL)
 
-        nt = (a = [1, 2], b = 3.0)
+        nt = (a=[1, 2], b=3.0)
         @test DynamicPPL.tovec(nt) == [1, 2, 3.0]
+
+        t = (2.0, [3.0, 4.0])
+        @test DynamicPPL.tovec(t) == [2.0, 3.0, 4.0]
     end
 
     @testset "unique_syms" begin