I just briefly reviewed the README docs, I believe the KlongPy is a custom language which transpiles to Python. The REPL block you are trying to interpret is the KlongPy REPL not a Python one.

Embedding KlongPy in a Python block would look more like this (also from the docs):

    from klongpy import KlongInterpreter
    import numpy as np

    data = np.array([1, 2, 3, 4, 5])
    klong = KlongInterpreter()
    # make the data NumPy array available to KlongPy code by passing it into the interpreter
    # we are creating a symbol in KlongPy called 'data' and assigning the external NumPy array value
    klong['data'] = data
    # define the average function in KlongPY
    klong('avg::{(+/x)%#x}')
    # call the average function with the external data and return the result.
    r = klong('avg(data)')
    print(r) # expected value: 3

Note the calls to "klong('<some-str-of-klong-syntax')".