getWhitespaceAtVerticalOffset(verticalOffset) {
        this._checkPendingChanges();
        verticalOffset = verticalOffset | 0;
        const candidateIndex = this.getWhitespaceIndexAtOrAfterVerticallOffset(verticalOffset);
        if (candidateIndex < 0) {
            return null;
        }
        if (candidateIndex >= this.getWhitespacesCount()) {
            return null;
        }
        const candidateTop = this.getVerticalOffsetForWhitespaceIndex(candidateIndex);
        if (candidateTop > verticalOffset) {
            return null;
        }
        const candidateHeight = this.getHeightForWhitespaceIndex(candidateIndex);
        const candidateId = this.getIdForWhitespaceIndex(candidateIndex);
        const candidateAfterLineNumber = this.getAfterLineNumberForWhitespaceIndex(candidateIndex);
        return {
            id: candidateId,
            afterLineNumber: candidateAfterLineNumber,
            verticalOffset: candidateTop,
            height: candidateHeight
        };
    }
Get exactly the whitespace that is layouted at `verticalOffset`.

@param verticalOffset The vertical offset.
@return Precisely the whitespace that is layouted at `verticaloffset` or null.