add method to get correct time_series_type

src/utils/powersystems_utils.jl

@@ -337,3 +337,22 @@ function _get_piecewise_incrementalcurve_per_system_unit(
     y_coords_normalized = y_coords .* system_base_power
     return PSY.PiecewiseStepData(x_coords_normalized, y_coords_normalized)
 end
+
+function get_deterministic_time_series_type(sys::PSY.System)
+    time_series_types = IS.get_time_series_counts_by_type(sys.data)
+    @show existing_types = Set(d["type"] for d in time_series_types)
+    if Set(["Deterministic", "DeterministicSingleTimeSeries"]) ∈ existing_types
+        error(
+            "The System contains a combination of forecast data and transformed time series data. Currently this is not supported.",
+        )
+    end
+    if "Deterministic" ∈ existing_types
+        return PSY.Deterministic
+    elseif "DeterministicSingleTimeSeries" ∈ existing_types
+        return PSY.DeterministicSingleTimeSeries
+    else
+        error(
+            "The System does not contain any forecast data or transformed time series data.",
+        )
+    end
+end