private byte[] bytes(final int size, final int zerofill) {
    final byte[] bytes = new byte[size];
    random.nextBytes(bytes);
    Arrays.fill(bytes, 0, zerofill, (byte) 0x0);
    return bytes;
  }
Creates a byte sequence with leading zeros.

@param size The size of the byte array to return
@param zerofill The number of lower-order bytes to fill with zero (creating a smaller big
    endian integer value)
@return the array of bytes.
ethereum/core/src/test-support/java/org/hyperledger/besu/ethereum/core/BlockDataGenerator.java