Add MUSE method and spec

app/models/gql/query_interface/lookup.rb

@@ -68,6 +68,10 @@ def energy_use_nodes(keys)
         energy_graph_helper.use_nodes(keys)
       end
 
+      def molecule_use_nodes(keys)
+        molecule_graph_helper.use_nodes(keys)
+      end
+
       def group_energy_nodes(keys)
         energy_graph_helper.group_nodes(keys)
       end

app/models/gql/runtime/functions/lookup.rb

@@ -143,6 +143,11 @@ def USE(*keys)
         scope.energy_use_nodes(keys)
       end
 
+      # Returns an Array of {Qernel::Node} for given molecule use. See USE.
+      def MUSE(*keys)
+        scope.molecule_use_nodes(keys)
+      end
+
       # Returns an Array of {Qernel::Carrier} for given key(s). Returns carriers belonging to the
       # energy graph.
       #

spec/fixtures/etsource/graphs/molecules/nodes/m_right_one.ad

@@ -1,2 +1,3 @@
 - output.co2 = 1.0
+- use = energetic
 ~ demand = 0.75

spec/fixtures/etsource/graphs/molecules/nodes/m_right_two.ad

@@ -1,2 +1,3 @@
 - output.co2 = 1.0
+- use = non_energetic
 ~ demand = 0.25

spec/models/gql/runtime/functions/lookup_spec.rb

@@ -74,5 +74,35 @@ module Gql::Runtime::Functions
         expect(result).to eq(10.0)
       end
     end
+
+    # MUSE
+    # ----
+
+    describe 'MUSE(energetic)' do
+      it 'returns [Node(m_right_one)]' do
+        expect(result).to eq([molecule_graph.node(:m_right_one)])
+      end
+    end
+
+    describe 'MUSE(non_energetic)' do
+      it 'returns [Node(m_right_two)]' do
+        expect(result).to eq([molecule_graph.node(:m_right_two)])
+      end
+    end
+
+    describe 'MUSE(energetic, non_energetic)' do
+      it 'returns [Node(m_right_one), Node(m_right_two)]' do
+        expect(result).to eq([
+          molecule_graph.node(:m_right_one),
+          molecule_graph.node(:m_right_two)
+        ])
+      end
+    end
+
+    describe 'MUSE(undefined)' do
+      it 'returns []' do
+        expect(result).to eq([])
+      end
+    end
   end
 end