Add docstrings for stringio

Author: seisman

pygmt/helpers/utils.py

@@ -195,7 +195,7 @@ def data_kind(  # noqa: PLR0911
     r"""
     Check the kind of data that is provided to a module.
 
-    The ``data`` argument can be in any type. Following data kinds are recognized:
+    The ``data`` argument can be in any types. Following data kinds are recognized:
 
     - ``"arg"``: data is ``None`` and ``required=False``, or bool, int, float,
       representing an optional argument, used for dealing with optional virtual files
@@ -205,6 +205,7 @@ def data_kind(  # noqa: PLR0911
       (e.g., geopandas.GeoDataFrame or shapely.geometry)
     - ``"grid"``: a :class:`xarray.DataArray` object that is not 3-D
     - ``"image"``: a 3-D :class:`xarray.DataArray` object
+    - ``"stringio"``: a :class:`io.StringIO` object
     - ``"matrix"``: anything that is not None
     - ``"vectors"``: data is ``None`` and ``required=True``