Consolidate MapData.from_multiple_map_data into MapData.from_multiple_data (facebook#4410)

Summary:

**Context**:

The following very similar methods exist:
* `Data.from_multiple_data`: Combines multiple `Data` (not MapData) into one `Data`
* `MapData.from_multiple_data`: Converts any data arguments into `MapData` if they are not already and then calls `MapData.from_multiple_map_data`
* `MapData.from_multiple_map_data`: Combines `MapData`s into one `MapData`


**This PR**:
* Removes `MapData.from_multiple_map_data`; `MapData.from_multiple_data` should now be used

Reviewed By: Balandat

Differential Revision: D84066098

Author: esantorella

ax/core/map_data.py

@@ -10,7 +10,7 @@
 import warnings
 
 from bisect import bisect_right
-from collections.abc import Iterable, Sequence
+from collections.abc import Iterable
 from logging import Logger
 from math import nan
 from typing import Any
@@ -119,23 +119,6 @@ def true_df(self) -> pd.DataFrame:
     def required_columns(self) -> set[str]:
         return super().required_columns().union({MAP_KEY})
 
-    @staticmethod
-    def from_multiple_map_data(data: Sequence[MapData]) -> MapData:
-        if len(data) == 0:
-            return MapData()
-
-        # Avoid concatenating empty dataframes which logs a warning.
-        non_empty_dfs = [datum.map_df for datum in data if not datum.map_df.empty]
-        df = (
-            pd.concat(non_empty_dfs)
-            if len(non_empty_dfs) > 0
-            else pd.DataFrame(
-                columns=[*{col for datum in data for col in datum.required_columns()}]
-            )
-        )
-
-        return MapData(df=df)
-
     @property
     def map_df(self) -> pd.DataFrame:
         return self.full_df
@@ -147,12 +130,26 @@ def from_multiple_data(cls, data: Iterable[Data]) -> MapData:
 
         If no "step" column is present, it will be filled in with NaNs.
         """
-        map_datas = [
-            (cls(df=datum.df) if not isinstance(datum, MapData) else datum)
+        map_dfs = [
+            datum.full_df
+            if isinstance(datum, MapData)
+            else datum.df.assign(**{MAP_KEY: nan})
             for datum in data
+            if not datum.full_df.empty
         ]
 
-        return cls.from_multiple_map_data(data=map_datas)
+        if len(map_dfs) == 0:
+            return MapData()
+
+        # Avoid concatenating empty dataframes which logs a warning.
+        df = (
+            pd.concat(map_dfs)
+            if len(map_dfs) > 0
+            else pd.DataFrame(
+                columns=[*{col for datum in data for col in datum.required_columns()}]
+            )
+        )
+        return MapData(df=df)
 
     @property
     def df(self) -> pd.DataFrame:

ax/core/tests/test_map_data.py

@@ -8,6 +8,7 @@
 
 import numpy as np
 import pandas as pd
+from ax.core.data import Data
 from ax.core.map_data import MAP_KEY, MapData
 from ax.core.tests.test_data import TestDataBase
 from ax.utils.common.testutils import TestCase
@@ -108,13 +109,22 @@ def test_init(self) -> None:
 
     def test_combine(self) -> None:
         with self.subTest("From no MapDatas"):
-            data = MapData.from_multiple_map_data([])
+            data = MapData.from_multiple_data([])
+            self.assertIsInstance(data, MapData)
             self.assertEqual(data.map_df.size, 0)
 
         with self.subTest("From two MapDatas"):
-            mmd_double = MapData.from_multiple_map_data([self.mmd, self.mmd])
+            mmd_double = MapData.from_multiple_data([self.mmd, self.mmd])
+            self.assertIsInstance(mmd_double, MapData)
             self.assertEqual(mmd_double.map_df.size, 2 * self.mmd.map_df.size)
 
+        with self.subTest("From Datas"):
+            data = Data(df=self.mmd.df)
+            map_data = MapData.from_multiple_data([data])
+            self.assertIsInstance(map_data, MapData)
+            data = Data.from_multiple_data([data])
+            self.assertEqual(len(data.full_df), len(map_data.full_df))
+
     def test_upcast(self) -> None:
         fresh = MapData(df=self.df)
         # Assert df is not cached before first call

ax/metrics/branin_map.py

@@ -130,7 +130,7 @@ def fetch_trial_data(
 
                 datas.append(MapData(df=df))
 
-            return Ok(value=MapData.from_multiple_map_data(datas))
+            return Ok(value=MapData.from_multiple_data(data=datas))
 
         except Exception as e:
             return Err(