public BigInteger readBigIntegerLE(int len, boolean unsigned) throws IOException {
        return readBigIntegerLE(input, bufferAllocator.allocate(len), len, unsigned);
    }
Reads a big integer value in little-endian from the internal input stream.
@param len - number of bytes to read
@param unsigned - whether the value is unsigned
@return big integer value
@throws IOException when IO error occurs
client-v2/src/main/java/com/clickhouse/client/api/data_formats/internal/BinaryStreamReader.java