def test_drop_obs_column():
    adata = ad.AnnData(np.array(X_list), obs=obs_dict, dtype="int32")

    subset = adata[:2]
    assert subset.is_view
    # returns a copy of obs
    assert subset.obs.drop(columns=["oanno1"]).columns.tolist() == ["oanno2", "oanno3"]
    assert subset.is_view
    # would modify obs, so it should actualize subset and not modify adata
    subset.obs.drop(columns=["oanno1"], inplace=True)
    assert not subset.is_view
    assert subset.obs.columns.tolist() == ["oanno2", "oanno3"]

    assert adata.obs.columns.tolist() == ["oanno1", "oanno2", "oanno3"]
def zoneplan(wdg, ax=0):
    """plot zone plan of winding wdg"""
    from matplotlib.patches import Rectangle
    upper, lower = wdg.zoneplan()
    Qb = len([n for l in upper for n in l])
    from femagtools.windings import coil_color
    rh = 0.5
    if lower:
        yl = rh
        ymax = 2*rh + 0.2
    else:
        yl = 0
        ymax = rh + 0.2
    if ax == 0:
        ax = plt.gca()
    ax.axis('off')
    ax.set_xlim([-0.5, Qb-0.5])
    ax.set_ylim([0, ymax])
    ax.set_aspect(Qb/6+0.3)

    for i, p in enumerate(upper):
        for x in p:
            ax.add_patch(Rectangle((abs(x)-1.5, yl), 1, rh,
                                   facecolor=coil_color[i],
                                   edgecolor='white', fill=True))
            s = f'+{i+1}' if x > 0 else f'-{i+1}'
            ax.text(abs(x)-1, yl+rh/2, s, color='black',
                    ha="center", va="center")
    for i, p in enumerate(lower):
        for x in p:
            ax.add_patch(Rectangle((abs(x)-1.5, yl-rh), 1, rh,
                                   facecolor=coil_color[i],
                                   edgecolor='white', fill=True))
            s = f'+{i+1}' if x > 0 else f'-{i+1}'
            ax.text(abs(x)-1, yl-rh/2, s, color='black',
                    ha="center", va="center")

    yu = yl+rh
    step = 1 if Qb < 25 else 2
    if lower:
        yl -= rh
    margin = 0.05
    ax.text(-0.5, yu+margin, f'Q={wdg.Q}, p={wdg.p}, q={round(wdg.q,4)}',
            ha='left', va='bottom', size=15)
    for i in range(0, Qb, step):
        ax.text(i, yl-margin, f'{i+1}', ha="center", va="top")