Add columns to save.

src/dgbowl_schemas/dgpost/recipe_2_1/save.py

@@ -1,5 +1,5 @@
 from pydantic import BaseModel, Field
-from typing import Literal
+from typing import Optional, Literal, Sequence
 
 
 class Save(BaseModel, extra="forbid", populate_by_name=True):
@@ -11,7 +11,7 @@ class Save(BaseModel, extra="forbid", populate_by_name=True):
     as_: str = Field(alias="as")
     """Path to which the table is stored."""
 
-    type: Literal["pkl", "json", "xlsx", "csv", "nc"] = None
+    type: Optional[Literal["pkl", "json", "xlsx", "csv", "nc"]] = None
     """
     Type of the output file.
 
@@ -23,6 +23,19 @@ class Save(BaseModel, extra="forbid", populate_by_name=True):
         not be used for chaining of :mod:`dgpost` runs.
     """
 
+    columns: Optional[Sequence[str]] = None
+    """
+    Columns to be exported. By default (``None``), all columns from the specified ``table``
+    will be exported.
+
+    .. note::
+
+       If any of the columns supplied is not present in the table, a warning will be
+       printed by :mod:`dgpost`.
+
+    """
+
+
     sigma: bool = True
     """Whether uncertainties/error estimates in the data should be stripped. Particularly
     useful when exporting into ``xlsx`` or ``csv``."""