Change append to concat in pandas dataframes to be compatible with Pandas >=2.0.0

[brunomorampc]

See issue https://stackoverflow.com/questions/75956209/dataframe-object-has-no-attribute-append

[musaddiq-ashfaq]

In which file do you want this change?

[brunomorampc]

Hi @musaddiq-ashfaq thanks for your interest!

For example here

hilo-mpc/hilo_mpc/modules/machine_learning/nn/nn.py

Line 322 in 5066265

data = self._data_sets[0].append(self._data_sets[1:], ignore_index=True, sort=False)

there might be other places though. Ideally one should run all tests and examples with pandas 2.0.0 and see where the problem occurs. I got the problem in that line by running this example https://github.com/hilo-mpc/examples/blob/main/nmpc_hybrid_bio.py