Allow meaningless variables in SingleReadout

src/components/readouts/single_readouts.jl

@@ -12,6 +12,18 @@ Represents an instantaneous `Readout` of the signal.
 It has no parameters or variables to set.
 """
 struct SingleReadout <: ReadoutComponent
+    SingleReadout(s::Symbol) = new()
+end
+
+function SingleReadout(; duration=nothing, kwargs...)
+    bad_keys = [key for (key, value) in pairs(kwargs) if !(isnothing(value) || (value isa Union{AbstractArray, Tuple} && all(isnothing.(value))))]
+    if length(bad_keys) > 0
+        error("SingleReadout does not expect any variables, yet it received $bad_keys.")
+    end
+    if !(duration in (nothing, :min, :max, 0, 0.))
+        error("SingleReadout did not expect a value for duration, yet received $duration.")
+    end
+    return SingleReadout(:prevent_loop)
 end
 
 duration(::SingleReadout) = 0.