How to use the node-opcua-basic-types.isValidInt64 function in node-opcua-basic-types

function isValidScalarVariant(dataType, value) {

    assert(value === null || DataType.Int64 === dataType || DataType.ByteString === dataType || DataType.UInt64 === dataType || !(value instanceof Array));
    assert(value === null || !(value instanceof Int32Array));
    assert(value === null || !(value instanceof Uint32Array));
    switch (dataType) {
        case DataType.NodeId:
            return ec.isValidNodeId(value);
        case DataType.String:
            return typeof value === "string" || utils.isNullOrUndefined(value);
        case DataType.Int64:
            return ec.isValidInt64(value);
        case DataType.UInt64:
            return ec.isValidUInt64(value);
        case DataType.UInt32:
            return ec.isValidUInt32(value);
        case DataType.Int32:
            return ec.isValidInt32(value);
        case DataType.UInt16:
            return ec.isValidUInt16(value);
        case DataType.Int16:
            return ec.isValidInt16(value);
        case DataType.Byte:
            return ec.isValidUInt8(value);
        case DataType.SByte:
            return ec.isValidInt8(value);
        case DataType.Boolean:
            return ec.isValidBoolean(value);

function isValidScalarVariant(dataType: DataType, value: any): boolean {

  assert(value === null
    || DataType.Int64 === dataType
    || DataType.ByteString === dataType
    || DataType.UInt64 === dataType
    || !(value instanceof Array));
  assert(value === null || !(value instanceof Int32Array));
  assert(value === null || !(value instanceof Uint32Array));
  switch (dataType) {
    case DataType.NodeId:
      return isValidNodeId(value);
    case DataType.String:
      return typeof value === "string" || utils.isNullOrUndefined(value);
    case DataType.Int64:
      return isValidInt64(value);
    case DataType.UInt64:
      return isValidUInt64(value);
    case DataType.UInt32:
      return isValidUInt32(value);
    case DataType.Int32:
      return isValidInt32(value);
    case DataType.UInt16:
      return isValidUInt16(value);
    case DataType.Int16:
      return isValidInt16(value);
    case DataType.Byte:
      return isValidUInt8(value);
    case DataType.SByte:
      return isValidInt8(value);
    case DataType.Boolean:
      return isValidBoolean(value);