Ragas fix for use of metrics argument (#177)

* small fix for ragas.py

Signed-off-by: aasavari <aasavari.dhananjay.kakne@intel.com>

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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* fixed error when metrics arg is used

Signed-off-by: aasavari <aasavari.dhananjay.kakne@intel.com>

---------

Signed-off-by: aasavari <aasavari.dhananjay.kakne@intel.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

evals/metrics/ragas/ragas.py

@@ -123,7 +123,7 @@ def measure(self, test_case: Dict):
                 else:
                     if metric == "AnswerRelevancy" and self.embeddings is None:
                         raise ValueError("AnswerRelevancy metric need provide embeddings model.")
-                    tmp_metrics.append(self.metrics_instances[metric])
+                    tmp_metrics.append(self.metric_instances[metric])
             self.metrics = tmp_metrics
         else:
             self.metrics = list(self.metric_instances.values())