add mock api response for get_pyrat_line_mutations

pyrat-api-line-mutations-response.json

@@ -0,0 +1,32 @@
+[
+    {
+        "id": 1,
+        "name": "Mut-A",
+        "status": "active",
+        "possible_grades": [
+            {"id": 5, "name": "het"}, 
+            {"id": 6, "name": "hom"}, 
+            {"id": 7, "name": "wt"}
+        ]
+    },
+    {
+        "id": 2,
+        "name": "Mut-B",
+        "status": "inactive",
+        "possible_grades": [
+            {"id": 5, "name": "het"}, 
+            {"id": 6, "name": "hom"}, 
+            {"id": 7, "name": "wt"}
+        ]
+    },
+    {
+        "id": 3,
+        "name": "Mut-C",
+        "status": "active",
+        "possible_grades": [
+            {"id": 5, "name": "het"}, 
+            {"id": 6, "name": "hom"}, 
+            {"id": 7, "name": "wt"}
+        ]
+    }
+]