try to fix docs

Author: isaacsas

docs/src/model_creation/compositional_modeling.md

@@ -95,7 +95,7 @@ reactions *only* within a given system (i.e. ignoring subsystems), we can use
 Catalyst.get_species(rn)
 ```
 ```@example ex1
-Catalyst.parameters_toplevel(rn)
+Catalyst.get_ps(rn)
 ```
 ```@example ex1
 Catalyst.get_rxs(rn)
@@ -110,11 +110,6 @@ parameters(rn)
 ```@example ex1
 reactions(rn)   # or equations(rn)
 ```
-!!! note
-  Previously, `ModelingToolkit.get_ps(rn)` was recommended (rather than `Catalyst.parameters_toplevel(rn)`).
-  While it can still be used, due to an update in ModelingToolkit, `get_ps` now also returns potential
-  initialisation parameters (which are added to the model by ModelingToolkit, not the user).
-
 If we want to collapse `rn` down to a single system with no subsystems we can use
 ```@example ex1
 flatrn = Catalyst.flatten(rn)

docs/src/model_creation/constraint_equations.md

@@ -43,16 +43,19 @@ eq = [D(V) ~ λ * V]
 @named osys = ODESystem(eq, t)
 
 # build the ReactionSystem with no protein initially
-rn = @reaction_network begin
+rn = @network_component begin
     @species P(t) = 0.0
     $V,   0 --> P
     1.0, P --> 0
 end
 ```
 Notice, here we interpolated the variable `V` with `$V` to ensure we use the
-same symbolic unknown variable in the `rn` as we used in building `osys`. See the
-doc section on [interpolation of variables](@ref
-dsl_advanced_options_symbolics_and_DSL_interpolation) for more information.
+same symbolic unknown variable in the `rn` as we used in building `osys`. See
+the doc section on [interpolation of variables](@ref
+dsl_advanced_options_symbolics_and_DSL_interpolation) for more information. We
+also use `@network_component` instead of `@reaction_network` as when merging
+systems together Catalyst requires that the systems have not been marked as
+`complete` (which indicates to Catalyst that a system is finalized).
 
 We can now merge the two systems into one complete `ReactionSystem` model using
 [`ModelingToolkit.extend`](@ref):

docs/src/model_creation/reactionsystem_content_accessing.md

@@ -225,12 +225,12 @@ Similarly, `parameters` retrieves five different parameters. Here, we note that
 parameters(rs)
 ```
 
-If we wish to retrieve the species (or parameters) that are specifically contained in the top-level system (and not only indirectly through its subsystems), we can use the `Catalyst.get_species` (or `Catalyst.parameters_toplevel`) functions:
+If we wish to retrieve the species (or parameters) that are specifically contained in the top-level system (and not only indirectly through its subsystems), we can use the `Catalyst.get_species` (or `ModelingToolkit.getps`) functions:
 ```@example model_accessing_hierarchical
 Catalyst.get_species(rs)
 ```
 ```@example model_accessing_hierarchical
-Catalyst.parameters_toplevel(rs)
+ModelingToolkit.get_ps(rs)
 ```
 Here, our top-level model contains a single parameter (`kₜ`), and two the two versions of the `Xᵢ` species. These are all the symbolic variables that occur in the transportation reaction (`@kₜ, $(nucleus_sys.Xᵢ) --> $(cytoplasm_sys.Xᵢ)`), which is the only reaction of the top-level system. We can apply these functions to the systems as well. However, when we do so, the systems' names are not prepended:
 ```@example model_accessing_hierarchical
@@ -248,8 +248,3 @@ Other examples of similar pairs of functions are `get_unknowns` and `unknowns`,
 
 !!! note
     Due to the large number of available accessor functions, most `get_` functions are not directly exported by Catalyst. Hence, these must be used as `Catalyst.get_rxs`, rather than `get_rxs` directly. Again, a full list of accessor functions and instructions on how to use them can be found in [Catalyst's API](@ref api).
-
-!!! note
-  Previously, `ModelingToolkit.get_ps(rn)` was recommended (rather than `Catalyst.parameters_toplevel(rn)`).
-  While it can still be used, due to an update in ModelingToolkit, `get_ps` now also returns potential
-  initialisation parameters (which are added to the model by ModelingToolkit, not the user).

src/reactionsystem.jl

@@ -1445,7 +1445,7 @@ end
 
 function complete_check(sys, method)
     if MT.iscomplete(sys)  
-        error("$method requires systems to not be marked complete, but system: $(MT.get_name(sys)) is marked complete.")
+        error("$method with one or more `ReactionSystem`s requires systems to not be marked complete, but system: $(MT.get_name(sys)) is marked complete.")
     end
     nothing
 end