typefix: add pd.Series[str] as typehint to avoid mypy error

Author: randomseed42

src/bokeh_sampledata/browsers.py

@@ -38,7 +38,7 @@
 
 def _read_data() -> pd.DataFrame:
     df = package_csv("browsers_nov_2013.csv", names=("Version", "Share"), skiprows=1)
-    versions = df["Version"].map(lambda x: x.rsplit(" ", 1))
+    versions: pd.Series[str] = df["Version"].map(lambda x: x.rsplit(" ", 1))
     df["Browser"] = versions.map(lambda x: x[0])
     df["VersionNumber"] = versions.map(lambda x: x[1] if len(x) == 2 else "0")
     return df