Allow concatenating BaseRaw objects

Author: cbrnr

mwe.py

@@ -0,0 +1,15 @@
+import numpy as np
+
+import mne
+
+sfreq = 100.0
+ch_names = ["EEG 001", "EEG 002"]
+ch_types = ["eeg"] * 2
+info = mne.create_info(ch_names=ch_names, sfreq=sfreq, ch_types=ch_types)
+data = np.random.randn(len(ch_names), 1000)
+
+raw_array = mne.io.RawArray(data, info)
+raw_array.save("temp_raw.fif", overwrite=True)
+raw_fiff = mne.io.read_raw_fif("temp_raw.fif", preload=True)
+
+mne.concatenate_raws([raw_fiff, raw_array])