NullValues
A comma separated list which is replaced with nulls if there are found in the CSV file.
データ型
string
デフォルト値
""
解説
When this property is set, any cell containing one of the specified values is interpreted as a null value.
For example, setting NullValues to "NaN,\N,N/A" causes all occurrences of these strings to be returned as "null".
This property is useful for normalizing placeholder text values into nulls during import.