force color to be a string

muon/_core/plot.py

@@ -22,7 +22,7 @@ def scatter(
     data: Union[AnnData, MuData],
     x: Optional[str] = None,
     y: Optional[str] = None,
-    color: Optional[Union[str, Sequence[str]]] = None,
+    color: Optional[str] = None,
     use_raw: Optional[bool] = None,
     layers: Optional[Union[str, Sequence[str]]] = None,
     **kwargs,
@@ -42,8 +42,8 @@ def scatter(
         x coordinate
     y : Optional[str]
         y coordinate
-    color : Optional[Union[str, Sequence[str]]], optional (default: None)
-        Keys for variables or annotations of observations (.obs columns),
+    color : Optional[str], optional (default: None)
+        Key for variables or annotations of observations (.obs columns),
         or a hex colour specification.
     use_raw : Optional[bool], optional (default: None)
         Use `.raw` attribute of the modality where a feature (from `color`) is derived from.
@@ -72,10 +72,10 @@ def scatter(
         if isinstance(color, str):
             color_obs = _get_values(data, color, use_raw=use_raw, layer=layers[2])
             color_obs = pd.DataFrame({color: color_obs})
-            color = [color]
         else:
-            # scanpy#311 / scanpy#1497 has to be fixed for this to work
-            color_obs = _get_values(data, color, use_raw=use_raw, layer=layers[2])
+            raise TypeError("Expected color to be a string.")
+
+
         color_obs.index = data.obs_names
         obs = pd.concat([obs, color_obs], axis=1, ignore_index=False)
 
@@ -86,14 +86,14 @@ def scatter(
     # and are now stored in .obs
     retval = sc.pl.scatter(ad, x=x, y=y, color=color, **kwargs)
     if color is not None:
-        for col in color:
-            try:
-                data.uns[f"{col}_colors"] = ad.uns[f"{col}_colors"]
-            except KeyError:
-                pass
+        try:
+            data.uns[f"{color}_colors"] = ad.uns[f"{color}_colors"]
+        except KeyError:
+            pass
     return retval
 
 
+
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