add concat

spec/API_specification/dataframe_api/__init__.py

@@ -1,6 +1,7 @@
 """
 Function stubs and API documentation for the DataFrame API standard.
 """
+from typing import Sequence
 
 from .column_object import *
 from .dataframe_object import *
@@ -12,3 +13,26 @@
 String representing the version of the DataFrame API specification to which the
 conforming implementation adheres.
 """
+
+def concat(dataframes: Sequence[DataFrame]) -> DataFrame:
+    """
+    Concatenate DataFrames vertically.
+
+    To concatenate horizontally, please use ``insert``.
+
+    Parameters
+    ----------
+    dataframes : Sequence[DataFrame]
+        DataFrames to concatenate.
+        Column names, ordering, and dtypes must match.
+
+    Notes
+    -----
+    The order in which the input DataFrames appear in
+    the output is preserved.
+
+    Returns
+    -------
+    DataFrame
+    """
+    ...

spec/API_specification/dataframe_api/dataframe_object.py

@@ -265,7 +265,7 @@ def sorted_indices(
             If a sequence, it must be the same length as `keys`,
             and determines the direction with which to use each
             key to sort by.
-        nulls_position : {'first', 'last'}
+        nulls_position : ``{'first', 'last'}``
             Whether null values should be placed at the beginning
             or at the end of the result.
             Note that the position of NaNs is unspecified and may