Assertion Error

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AssertionError                            Traceback (most recent call last)
<ipython-input-7-07466b6a31e5> in <module>
      1 for arrays in tree.iterate({"fj_pt": uproot.asarray(">f8", pt_buffer),
      2                             "fj_eta": uproot.asarray(">f8", eta_buffer)},
----> 3                            outputtype=tuple, entrysteps=5000):
      4     pass

~/software/miniconda3/envs/def/lib/python3.7/site-packages/uproot/tree.py in iterate(self, branches, entrysteps, outputtype, namedecode, reportentries, entrystart, entrystop, flatten, flatname, awkwardlib, cache, basketcache, keycache, executor, blocking)
    710                 else:
    711                     basketstart, basketstop = branch._basketstartstop(start, stop)
--> 712                     basket_itemoffset = branch._basket_itemoffset(interpretation, basketstart, basketstop, keycache)
    713                     basket_entryoffset = branch._basket_entryoffset(basketstart, basketstop)
    714 

~/software/miniconda3/envs/def/lib/python3.7/site-packages/uproot/tree.py in _basket_itemoffset(self, interpretation, basketstart, basketstop, keycache)
   1339         for j, key in enumerate(self._threadsafe_iterate_keys(keycache, True, basketstart, basketstop)):
   1340             i = basketstart + j
-> 1341             numitems = interpretation.numitems(key.border, self.basket_numentries(i))
   1342             basket_itemoffset.append(basket_itemoffset[-1] + numitems)
   1343         return basket_itemoffset

~/software/miniconda3/envs/def/lib/python3.7/site-packages/uproot/interp/numerical.py in numitems(self, numbytes, numentries)
    150         dtype, shape = _dtypeshape(self.fromdtype)
    151         quotient, remainder = divmod(numbytes, dtype.itemsize)
--> 152         assert remainder == 0
    153         return quotient
    154 

AssertionError: