bugfix: Process result files of the form (metric, value) as dictionar…

…ies or scalar with the column name score (microsoft#460)

The LocalEnv.run() function processed any results DataFrame containing a
single record as a scalar record. This change ensures that even if the
result file contains a single line of the form `(metric, value)`, it is
processed as a dictionary.

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Co-authored-by: Sergiy Matusevych <sergiy.matusevych@gmail.com>

mlos_bench/mlos_bench/environments/local/local_env.py

@@ -155,7 +155,7 @@ def run(self) -> Tuple[Status, Optional[dict]]:
  self._read_results_file, extra_paths=[temp_dir]))
 
  _LOG.debug("Read data:\n%s", data)
- if len(data) != 1:
+ if list(data.columns) == ["metric", "value"]:
  _LOG.warning(
  "Local run has %d rows: assume long format of (metric, value)", len(data))
  data = pandas.DataFrame([data.value.to_list()], columns=data.metric.to_list())