constructor(separator, nGramWidths, leftPad, rightPad, padWidth, preserveShortSequences){
        this.separator = (0, _tfjsCore.util).encodeString(separator);
        this.nGramWidths = nGramWidths;
        this.leftPad = (0, _tfjsCore.util).encodeString(leftPad);
        this.rightPad = (0, _tfjsCore.util).encodeString(rightPad);
        this.padWidth = padWidth;
        this.preserveShort = preserveShortSequences;
    }
The StringNGramsOp class creates ngrams from ragged string data.
The constructor contains all attributes related to the operation such as
padding widths and strings, and the compute function can be used to
compute the ngrams for different ragged tensor inputs.