refactor: don't check isparameter in check_variables and check_parameters

Author: AayushSabharwal

src/utils.jl

@@ -124,8 +124,6 @@ function check_parameters(ps, iv)
     for p in ps
         isequal(iv, p) &&
             throw(ArgumentError("Independent variable $iv not allowed in parameters."))
-        isparameter(p) ||
-            throw(ArgumentError("$p is not a parameter."))
     end
 end
 
@@ -153,8 +151,6 @@ function check_variables(dvs, iv)
             throw(ArgumentError("Independent variable $iv not allowed in dependent variables."))
         (is_delay_var(iv, dv) || occursin(iv, dv)) ||
             throw(ArgumentError("Variable $dv is not a function of independent variable $iv."))
-        isparameter(dv) &&
-            throw(ArgumentError("$dv is not an unknown. It is a parameter."))
     end
 end