When manually recording the name and age of each person entering a museum in a CSV file, the following code block is intended to read that CSV file and convert it into a DataFrame.

The schema is defined as

StructType([StructField('name', StringType()), StructField('age', IntegerType())])

df = spark.read.format(csv) .schema(schema) ___________________ .load(/tmp/logs.csv)

The code reads the CSV file with the schema and loads it into a DataFrame. What should fill the blank to ensure records with 'NA' in the 'age' column are excluded from the DataFrame?