don't die if types aren't importable

Change-Id: I8804bfdd0c1cde893768a33959d1a91b38109d74

recirq/otoc/loschmidt/tilted_square_lattice/analysis.py

@@ -127,15 +127,15 @@ def groupby_all_except(df: pd.DataFrame, *, y_cols: Sequence[Any], agg_func: Any
 
 
 def _results_to_dataframe(
-        results: ExecutableGroupResult,
-        func: Callable[[ExecutableResult, QuantumRuntimeConfiguration, SharedRuntimeInfo], Dict]
+        results: 'ExecutableGroupResult',
+        func: Callable[['ExecutableResult', 'QuantumRuntimeConfiguration', 'SharedRuntimeInfo'], Dict]
 ) -> pd.DataFrame:
     """Call a function on each result in an `ExecutableGroupResult` to construct a DataFrame."""
     return pd.DataFrame([func(result, results.runtime_configuration, results.shared_runtime_info)
                          for result in results.executable_results])
 
 
-def loschmidt_results_to_dataframe(results: ExecutableGroupResult) -> pd.DataFrame:
+def loschmidt_results_to_dataframe(results: 'ExecutableGroupResult') -> pd.DataFrame:
     """Process an `ExecutableGroupResult`.
 
     This function performs the data analysis using `to_ground_state_prob` and
@@ -150,11 +150,11 @@ def loschmidt_results_to_dataframe(results: ExecutableGroupResult) -> pd.DataFra
     we do U and/or its inverse.
     """
 
-    def _to_record(result: ExecutableResult,
-                   rt_config: QuantumRuntimeConfiguration,
-                   shared_rt_info: SharedRuntimeInfo) -> Dict:
+    def _to_record(result: 'ExecutableResult',
+                   rt_config: 'QuantumRuntimeConfiguration',
+                   shared_rt_info: 'SharedRuntimeInfo') -> Dict:
         success_prob = to_ground_state_prob(result.raw_data)
-        spec = cast(TiltedSquareLatticeLoschmidtSpec, result.spec)
+        spec = cast('TiltedSquareLatticeLoschmidtSpec', result.spec)
 
         record = {
             'run_id': shared_rt_info.run_id,