Fix Operator.eval() in case output pin 0 is not named "fields_contain…

…er" (#1527)

Signed-off-by: paul.profizi <paul.profizi@ansys.com>

src/ansys/dpf/core/outputs.py

@@ -112,6 +112,9 @@ def _get_given_output(self, input_type_name):
                         corresponding_pins.append(pin)
         return corresponding_pins
 
+    def __getitem__(self, index):
+        return self._outputs[index]
+
     def __str__(self):
         docstr = "Available outputs:\n"
         for output in self._outputs:

src/ansys/dpf/core/results.py

@@ -263,7 +263,12 @@ def eval(self):
         >>> fc = disp.on_all_time_freqs.eval()
 
         """
-        fc = self.__call__().outputs.fields_container()
+        outputs = self.__call__().outputs
+        if hasattr(outputs, "fields_container"):
+            fc = outputs.fields_container()
+        else:
+            # Support operators where the first output is not named "field_container"
+            fc = outputs[0]()
         if self._specific_fc_type == "shape":
             fc = ElShapeFieldsContainer(fields_container=fc._get_ownership(), server=fc._server)
         elif self._specific_fc_type == "body":