Fix single graph handling

pina/collector.py

@@ -104,10 +104,6 @@ class Collector:
                 # get data
                 keys = condition.__slots__
                 values = [getattr(condition, name) for name in keys]
-                values = [
-                    value.data if isinstance(value, Graph) else value
-                    for value in values
-                ]
                 self.data_collections[condition_name] = dict(zip(keys, values))
                 # condition now is ready
                 self._is_conditions_ready[condition_name] = True

pina/condition/condition_interface.py

@@ -115,3 +115,9 @@ class ConditionInterface(metaclass=ABCMeta):
                         raise ValueError(
                             "LabelTensor must have the same labels"
                         )
+
+    def __getattribute__(self, name):
+        to_return = super().__getattribute__(name)
+        if isinstance(to_return, (Graph, Data)):
+            to_return = [to_return]
+        return to_return