def METHOD_NAME():
    # Addresses a bug where partial bin-table dataframes were sliced incorrectly,
    # specifically when the pixel dataframe happened to be shorter than it. This
    # led to incorrect NaNs in the join output.
    #
    # This is different from the case where there are pixels from bins that do
    # not appear in the provided partial bin-table dataframe. This will lead to
    # NaNs in the join but the result will be correct because those bins were
    # missing from the input. However, we may want to raise an error in such
    # cases, or disallow partial bin-table inputs entirely.
    clr = api.Cooler(op.join(datadir, "hg19.GM12878-MboI.matrix.2000kb.cool"))
    pix = clr.matrix(as_pixels=True, balance=False).fetch("chr2").iloc[:50]
    bins_chr2 = clr.bins().fetch("chr2")
    assert len(bins_chr2) > len(pix)
    out = api.annotate(pix, bins_chr2)
    for col in ['chrom1', 'start1', 'end1', 'chrom2', 'start2', 'end2']:
        assert out[col].notnull().all()