public Output write(byte[] bytes, int offset, int length) {
    outputStream.write(bytes, offset, length);
    return this;
  }
Writes the byte array to the output with specified offset and fixed length.

@param bytes byte arrays to write to this output
@param offset the offset within the array of the first byte to be read. Must be non-negative
    and no larger than <tt>bytes.length</tt>
@param length the number of bytes to be read from the given array
@return this output
form/src/main/java/feign/form/multipart/Output.java