[BUG] Hist.fill does not accept scalars for sample argument

[nsmith-]

Take for example:

import hist
import numpy as np
h = hist.Hist.new.Regular(10, 0, 1, name="x").WeightedMean()

I can fill with

h.fill(x=np.array([0.1, 0.1, 0.2]), sample=np.array([1, 2, 3]), weight=np.array([1, 2, 3]))
h.fill(x=0.3, sample=np.array([4]), weight=1.)

etc. but not

>>> h.fill(x=0.3, sample=4, weight=1.)

---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-11-0e663158df79> in <module>
----> 1 h.fill(x=0.3, sample=4, weight=1.)

/usr/local/lib/python3.9/site-packages/hist/basehist.py in fill(self, weight, sample, threads, *args, **kwargs)
    233
    234         total_data = tuple(args) + tuple(data)  # Python 2 can't unpack twice
--> 235         return super().fill(*total_data, weight=weight, sample=sample, threads=threads)
    236
    237     def sort(

/usr/local/lib/python3.9/site-packages/boost_histogram/_internal/hist.py in fill(self, weight, sample, threads, *args)
    431
    432         if threads is None or threads == 1:
--> 433             self._hist.fill(*args_ars, weight=weight_ars, sample=sample_ars)
    434             return self
    435

ValueError: Sample array must be 1D

[JMulder99]

When using the Mean or WeightedMean accumulator, it will also raise this error when no sample argument is passed.
For Mean: TypeError: Sample key-argument (sample=) needs to be provided.
For WeightedMean: ValueError: Sample array must be 1D

In the documentation it states "you can add a sample argument".

N = 10000
zenith = np.random.random(size=N) - 1
energy = np.random.exponential(scale=1000, size=N)
weights = 1/ np.random.randint(1, 5, size=N)

h_area = hist.Hist(
    hist.axis.Regular(20, -1, 0, name="zenith", label="Zenith"),
    hist.axis.Regular(20, 0, 10000, name="energy", label="Energy")
    name="Area",
    label="h_area",
    storage=hist.storage.WeightedMean()
)
h_AREA_DETFLUX_mean.fill(
    zenith=zenith,
    energy=energy, 
    weight=weights,
)