DOC: fix imports in doc page

docs/src/AlgebraicPetri.md

@@ -6,14 +6,22 @@ You can construct a [`ContinuousResourceSharer`](@ref) from an Open Petri Net fo
 2. OpenLabelledPetriNet
 3. OpenLabelledReactionNet
 
-````@example
+````@example AlgPetri
+using AlgebraicPetri
+using AlgebraicDynamics
 Brusselator = LabelledPetriNet([:A, :B, :D, :E, :X, :Y],
   :t1 => (:A => (:X, :A)),
   :t2 => ((:X, :X, :Y) => (:X, :X, :X)),
   :t3 => ((:B, :X) => (:Y, :D, :B)),
   :t4 => (:X => :E)
 )
+````
 
+You just call the constructor for ContinuousResourceSharer on an Open Petri Net. 
+The constructor knows where to use labels or integers for the state variables.
+It also knows to get parameters from the ReactionNet and enclose them into the dynamics.
+
+````@example AlgPetri
 open_bruss = Open([:A, :D], Brusselator, [:A, :B])
 rs = ContinuousResourceSharer{Float64}(open_bruss)
 ````