def __setitem__(self, key, value, warn_stacklevel=2):
            if not isinstance(value, ReportSheet):
                raise ValueError(f"Expected ReportSheet object. Got {type(value).__name__} object instead.")
            if key in self.sheet_names():
                warnings.warn(f"Sheet '{key}' already exists in the report and will be reset",
                              stacklevel=warn_stacklevel)
            self.sheets[key] = value