solve doc format

Author: Fu-Jie

janitor/functions/concatenate_columns.py

@@ -25,19 +25,19 @@ def concatenate_columns(
 
         >>> import pandas as pd
         >>> import janitor
-        >>> df = pd.DataFrame({"a": [1, pd.NA, 5], "b": list("xyz")})
+        >>> df = pd.DataFrame({"a": [1, 3, 5], "b": list("xyz")})
         >>> df
-           a     b
-        0  1     x
-        1  <NA>  y
-        2  5     z
+           a  b
+        0  1  x
+        1  3  y
+        2  5  z
         >>> df.concatenate_columns(
         ...     column_names=["a", "b"], new_column_name="m",
         ... )
-           a     b  m
-        0  <NA>  x  x
-        1  3     y  3-y
-        2  5     z  5-z
+           a  b    m
+        0  1  x  1-x
+        1  3  y  3-y
+        2  5  z  5-z
 
     :param df: A pandas DataFrame.
     :param column_names: A list of columns to concatenate together.