fillMissingValues(replacement, columnNames) {
        return this.replace([NaN, undefined, null], replacement, columnNames);
    }
Return a DataFrame with missing values (undefined, NaN, null) fill with default value.
@param replacement The new value.
@param {Array} columnNames The columns to consider. All columns are considered by default.
@returns {DataFrame} A DataFrame with missing values replaced.
@example
df.fillMissingValues(0, ['id', 'name'])