[fix] add forgotten self

Author: salvadorblasco

src/libeq/data_structure.py

@@ -107,7 +107,7 @@ def __used_points(self) -> list[bool]:
         if self.ignored is None:
             return len(v_add)*[True]
         else:
-            return ~ignored
+            return ~self.ignored
 
 class PotentiometryOptions(BaseModel):
     titrations: List[PotentiometryTitrationsParameters] = []