add source code for MeanField and NoConstraints structures

Author: bvdmitri

src/plugins/variational_constraints/variational_constraints.jl

@@ -17,8 +17,12 @@ See also: [`BetheFactorization`](@ref)
 """
 struct MeanField end
 
+source_code(::MeanField) = "MeanField"
+
 struct NoConstraints end
 
+source_code(::NoConstraints) = "NoConstraints"
+
 include("variational_constraints_macro.jl")
 include("variational_constraints_engine.jl")
 

test/plugins/variational_constraints/variational_constraints_tests.jl

@@ -1160,4 +1160,10 @@ end
     @test occursin("q(x, y)", source)
     @test occursin("q(x)", source)
     @test occursin("q(y)", source)
+
+    mf_constraints = GraphPPL.MeanField()
+
+    source = GraphPPL.source_code(mf_constraints)
+
+    @test occursin("MeanField", source)
 end