Minor refactor to example code in test case

Rather than repeatedly retrieve parameter values from each simulation
context, it's simpler to retrieve each prior dictionary and retrieve the
parameter values directly when needed.

tests/test_sirv.py

@@ -67,44 +67,40 @@ def verify_prior_samples(contexts):
     each scenario are either identical (e.g., pathogen parameters) or differ
     (e.g., intervention parameters).
     """
-    baseline_ctx = contexts['Baseline']
-    reduce_R0_ctx = contexts['Reduce R0']
-    vaccination_ctx = contexts['Vaccination']
+    baseline_prior = contexts['Baseline'].data['prior']
+    reduce_R0_prior = contexts['Reduce R0'].data['prior']
+    vaccination_prior = contexts['Vaccination'].data['prior']
 
     # Verify that samples for baseline parameters are identical.
     baseline_parameters = ['R0', 'gamma']
     for parameter in baseline_parameters:
-        baseline_vals = baseline_ctx.data['prior'][parameter]
-        reduce_R0_vals = reduce_R0_ctx.data['prior'][parameter]
-        vaccination_vals = vaccination_ctx.data['prior'][parameter]
+        baseline_vals = baseline_prior[parameter]
+        reduce_R0_vals = reduce_R0_prior[parameter]
+        vaccination_vals = vaccination_prior[parameter]
         assert np.array_equal(baseline_vals, reduce_R0_vals)
         assert np.array_equal(baseline_vals, vaccination_vals)
 
     # Verify that vaccine parameter samples are different only for the
     # vaccination scenario.
     vacc_parameters = [
-        param
-        for param in baseline_ctx.data['prior'].keys()
-        if param.startswith('Vaccine_')
+        param for param in baseline_prior if param.startswith('Vaccine_')
     ]
     for parameter in vacc_parameters:
-        baseline_vals = baseline_ctx.data['prior'][parameter]
-        reduce_R0_vals = reduce_R0_ctx.data['prior'][parameter]
-        vaccination_vals = vaccination_ctx.data['prior'][parameter]
+        baseline_vals = baseline_prior[parameter]
+        reduce_R0_vals = reduce_R0_prior[parameter]
+        vaccination_vals = vaccination_prior[parameter]
         assert not np.array_equal(baseline_vals, vaccination_vals)
         assert np.array_equal(baseline_vals, reduce_R0_vals)
 
     # Verify that R0 parameter samples are different only for the R0 reduction
     # scenario.
     R0_parameters = [
-        param
-        for param in baseline_ctx.data['prior'].keys()
-        if param.startswith('R0_')
+        param for param in baseline_prior if param.startswith('R0_')
     ]
     for parameter in R0_parameters:
-        baseline_vals = baseline_ctx.data['prior'][parameter]
-        reduce_R0_vals = reduce_R0_ctx.data['prior'][parameter]
-        vaccination_vals = vaccination_ctx.data['prior'][parameter]
+        baseline_vals = baseline_prior[parameter]
+        reduce_R0_vals = reduce_R0_prior[parameter]
+        vaccination_vals = vaccination_prior[parameter]
         assert not np.array_equal(baseline_vals, reduce_R0_vals)
         assert np.array_equal(baseline_vals, vaccination_vals)