code: def to_observations_dataframe(self, sql_ctx, ts_col='timestamp', key_col='key', val_col='value'):
          
          ssql_ctx = sql_ctx._ssql_ctx
          jdf = self._jtsrdd.toObservationsDataFrame(ssql_ctx, ts_col, key_col, val_col)
          return DataFrame(jdf, sql_ctx)
docs: Returns a DataFrame of observations, each containing a timestamp, a key, and a value.
  
          Parameters
          ----------
          sql_ctx : SQLContext
          ts_col : string
              The name for the timestamp column.
          key_col : string
              The name for the key column.
          val_col : string
              The name for the value column.