EnsParTable: fix key type to Symbol

Co-authored-by: Maximilian-Stefan-Ernst <34346372+Maximilian-Stefan-Ernst@users.noreply.github.com>

Author: alyst

src/frontend/specification/EnsembleParameterTable.jl

@@ -2,8 +2,8 @@
 ### Types
 ############################################################################################
 
-struct EnsembleParameterTable{K} <: AbstractParameterTable
-    tables::Dict{K, ParameterTable}
+struct EnsembleParameterTable <: AbstractParameterTable
+    tables::Dict{Symbol, ParameterTable}
     params::Vector{Symbol}
 end
 
@@ -13,7 +13,7 @@ end
 
 # constuct an empty table
 EnsembleParameterTable(::Nothing; params::Union{Nothing, Vector{Symbol}} = nothing) =
-    EnsembleParameterTable{Symbol}(
+    EnsembleParameterTable(
         Dict{Symbol, ParameterTable}(),
         isnothing(params) ? Symbol[] : copy(params),
     )
@@ -32,11 +32,11 @@ function EnsembleParameterTable(
     end
 
     # convert each model specification to ParameterTable
-    partables = Dict{K, ParameterTable}(
-        group => convert(ParameterTable, spec; params) for
+    partables = Dict{Symbol, ParameterTable}(
+        Symbol(group) => convert(ParameterTable, spec; params) for
         (group, spec) in pairs(spec_ensemble)
     )
-    return EnsembleParameterTable{K}(partables, params)
+    return EnsembleParameterTable(partables, params)
 end
 
 ############################################################################################