fix: add temporary error message when simplifying systems with noise_eqs

Author: AayushSabharwal

src/systems/systems.jl

@@ -66,6 +66,11 @@ end
 
 function __structural_simplify(sys::AbstractSystem, io = nothing; simplify = false,
         kwargs...)
+    # TODO: convert noise_eqs to brownians for simplification
+    if has_noise_eqs(sys) && !isempty(get_noise_eqs(sys))
+        throw(ArgumentError("Cannot simplify systems with `noise_eqs`"))
+    end
+
     sys = expand_connections(sys)
     state = TearingState(sys)