even better flow bin handling

tools/read_hist.py

+import numpy as np
+import matplotlib.pyplot as plt
+import boost_histogram as bh
+import operator
+import functools
+
+def read_hist(filename):
+    """
+    read numpy file produced with CORSIKA 8's save_hist() function into
+    boost-histogram object.
+    """
+
+    d = np.load(filename)
+    axistypes = d['axistypes'].view('c')
+    overflow = d['overflow']
+    underflow = d['underflow']
+    
+    axes = []
+    for i, (at, has_overflow, has_underflow) in enumerate(zip(axistypes, overflow, underflow)):
+        if at == b'c':
+            axes.append(bh.axis.Variable(d[f'binedges_{i}'], overflow=has_overflow, underflow=has_underflow))
+        elif at == b'd':
+            axes.append(bh.axis.IntCategory(d[f'bins_{i}'], growth=(not has_overflow)))
+        
+    h = bh.Histogram(*axes)
+    h.view(flow=True)[:] = d['data']
+    
+    return h
+