fix: Fix mocked methods

Author: alecandido

src/qibolab/_core/instruments/qblox/mock/cluster.py

@@ -12,8 +12,12 @@ def __init__(self, idx: int, ancestors: list) -> None:
         self.register = {"calls": []}
         self.ancestors = [self] + ancestors
 
+    @property
+    def seq_idx(self):
+        return self.idx
+
     def __getattribute__(self, name: str):
-        if name in ["idx", "register", "ancestors"]:
+        if name in ["idx", "register", "ancestors", "seq_idx"]:
             return super().__getattribute__(name)
 
         log: dict["str", Any] = {"name": name}
@@ -131,3 +135,6 @@ def get_acquisition_status(self, slot: int, sequencer: int, *, timeout: int):
 
     def get_acquisitions(self, slot: int, sequencer: int) -> dict:
         return {}
+
+    def reference_source(self, value=None) -> None:
+        pass