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 _get_unique_constraints(self, table):
    """Retrieve information about existing unique constraints of the table

    This feature is needed for _recreate_table() to work properly.
    Unfortunately, it's not available in sqlalchemy 0.7.x/0.8.x.

    """

    data = table.metadata.bind.execute(
        """SELECT sql
           FROM sqlite_master
           WHERE
               type='table' AND
               name=:table_name""",
        table_name=table.name
    ).fetchone()[0]

    UNIQUE_PATTERN = "CONSTRAINT (\w+) UNIQUE \(([^\)]+)\)"
    return [
        UniqueConstraint(
            *[getattr(table.columns, c.strip(' "')) for c in cols.split(",")],
            name=name
        )
        for name, cols in re.findall(UNIQUE_PATTERN, data)
    ]