function isValidVertex(h3Index) {
    const [lower, upper] = h3IndexToSplitLong(h3Index);
    return Boolean(H3.isValidVertex(lower, upper));
}
Returns true if the input is a valid vertex index.
@static
@param {H3IndexInput} h3Index An index to test for being a vertex index
@returns {boolean} True if the index represents a vertex