[Python] Pylance error message when writing byte string from dictionary to serial port

I need to send a byte string command over serial port, and read this command from a dictionary.
Pylance throws an error, though everything is working fine.
Writing the byte string command directly to serial port, there is no error.

# No error writing byte string as an argument -----------------------
cmd_direct = b'AT\r'
comport.write(cmd_direct)

# Error reading byte string from dictionary first -----------------------
cmd_dict = {
"cmd1": b'AT\r',
"cmd2": b'AT+HTTPINIT\r'
}

cmd_value_dict = cmd_dict.get("cmd1")
comport.write(cmd_value_dict)
# ^^^^^^^^^^
# Argument of type "bytes | None" cannot be assigned to parameter "b" of type "ReadableBuffer" in function "write"
# Type "bytes | None" is not assignable to type "ReadableBuffer"
# "None" is incompatible with protocol "Buffer"
# "__buffer__" is not present Pylancer(eportArgumentType)
# (variable) cmd_value_dict: bytes | None


The debugger in both cases shows exactly the same value when sending, so why is this error?
I'm just a beginner on python and I don't understand the error message.
Maybe someone can explain, what it means and how to avoid (though it's actually working).

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