Currently there's no way to send bytes directly from one algorithm to another.

The current "workaround" is to build the bytes output then use base64 encoding, use a string based type to write the data to the output and on the other end load it back from string.

Example of working code:

Output:

    obj = dict(field1=data.value*2, field2=data.value)
    dumped = pickle.dumps(obj)  # binary
    encoded = base64.b64encode(dumped)  # base64 bytes
    string = encoded.decode("ascii")  # "stringified"
    outputs["out_data"].write({"value": string})

WARNING Do not call str(encoded), it won't be a "real string":

example = b"whatever"
example_str = str(example)
example_str
#  output is "b'whatever'"

Input:

    in_data = inputs["in_data"].data  # string data
    decoded = base64.b64decode(in_data.value)  # decode to bytes
    obj = pickle.loads(decoded)  # obj is a dict and can be read

This issue tracks the implementation of the support for the python bytes type.