TypeError: string argument without an encoding

You are probably only one step away from the answer.

See bytearray() and bytes for the function usage (you may need to change python version of the document).

And it says:

The optional source parameter can be used to initialize the array in a few different ways:

• If it is a string, you must also give the encoding (and optionally, errors) parameters; bytearray() then converts the string to bytes using str.encode().
• If it is an integer, the array will have that size and will be initialized with null bytes.
• If it is an object conforming to the buffer interface, a read-only buffer of the object will be used to initialize the bytes array.
• If it is an iterable, it must be an iterable of integers in the range 0 <= x < 256, which are used as the initial contents of the array.

Notice that the square bracket indicates that those parameters can be omitted, it is not an array type of python language.

So you should use bytes(create_jsonlines(source), encoding='utf8').

You are not using the bytes function correctly. Check this:

>>> a = "hi"
>>> bytes(a, encoding='utf8')
b'hi'

You can try:

bytes((create_jsonlines(source)), encoding='utf8')

encoding is the argument of the bytes function, and you are using it outside of that function.

When you read any python function docs as

bytes([source[, encoding[, errors]]])

square brackets represent that those parameters are optional. multiple square brackets inside another mean they are next level of option params. For example

bytes([source....

means we can call bytes as byes() itself as [source] is optional here

bytes() -> empty bytes object

bytes(22)

Here 22 is being passed as the source

read this for more details about bytes and its params

https://docs.python.org/3/library/stdtypes.html#bytes