How to use the gsd.hoomd.Snapshot function in gsd

def test_defaults(tmp_path, open_mode):
    """Test that the property defaults are properly set."""
    snap = gsd.hoomd.Snapshot()
    snap.particles.N = 2
    snap.bonds.N = 3
    snap.angles.N = 4
    snap.dihedrals.N = 5
    snap.impropers.N = 6
    snap.constraints.N = 4
    snap.pairs.N = 7

    with gsd.hoomd.open(name=tmp_path / "test_defaults.gsd",
                        mode=open_mode.write) as hf:
        hf.append(snap)

    with gsd.hoomd.open(name=tmp_path / "test_defaults.gsd",
                        mode=open_mode.read) as hf:
        s = hf.read_frame(0)

def test_state(tmp_path, open_mode):
    """Test the state chunks."""
    snap0 = gsd.hoomd.Snapshot()

    snap0.state['hpmc/sphere/radius'] = [2.0]
    snap0.state['hpmc/sphere/orientable'] = [1]

    snap1 = gsd.hoomd.Snapshot()

    snap1.state['hpmc/convex_polyhedron/N'] = [3]
    snap1.state['hpmc/convex_polyhedron/vertices'] = [[-1, -1, -1], [0, 1, 1],
                                                      [1, 0, 0]]

    with gsd.hoomd.open(name=tmp_path / "test_state.gsd",
                        mode=open_mode.write) as hf:
        hf.extend([snap0, snap1])

    with gsd.hoomd.open(name=tmp_path / "test_state.gsd",
                        mode=open_mode.read) as hf:

def test_log(tmp_path, open_mode):
    """Test the log chunks."""
    snap0 = gsd.hoomd.Snapshot()

    snap0.log['particles/net_force'] = [[1, 2, 3], [4, 5, 6]]
    snap0.log['particles/pair_lj_energy'] = [0, -5, -8, -3]
    snap0.log['value/potential_energy'] = [10]
    snap0.log['value/pressure'] = [-3]

    snap1 = gsd.hoomd.Snapshot()

    snap1.log['particles/pair_lj_energy'] = [1, 2, -4, -10]
    snap1.log['value/pressure'] = [5]

    with gsd.hoomd.open(name=tmp_path / "test_log.gsd",
                        mode=open_mode.write) as hf:
        hf.extend([snap0, snap1])

    with gsd.hoomd.open(name=tmp_path / "test_log.gsd",
                        mode=open_mode.read) as hf:
        assert len(hf) == 2
        s = hf.read_frame(0)

        numpy.testing.assert_array_equal(s.log['particles/net_force'],
                                         snap0.log['particles/net_force'])
        numpy.testing.assert_array_equal(s.log['particles/pair_lj_energy'],

def test_fallback2(tmp_path, open_mode):
    """Test additional fallback behaviors."""
    snap0 = gsd.hoomd.Snapshot()
    snap0.configuration.step = 1
    snap0.configuration.dimensions = 3
    snap0.particles.N = 2
    snap0.particles.mass = [2, 3]

    snap1 = gsd.hoomd.Snapshot()
    snap1.configuration.step = 2
    snap1.particles.N = 2
    snap1.particles.position = [[1, 2, 3], [4, 5, 6]]

    with gsd.hoomd.open(name=tmp_path / "test_fallback2.gsd",
                        mode=open_mode.write) as hf:
        hf.extend([snap0, snap1])

    with gsd.hoomd.open(name=tmp_path / "test_fallback2.gsd",
                        mode=open_mode.read) as hf:
        assert len(hf) == 2

        s = hf.read_frame(1)
        numpy.testing.assert_array_equal(s.particles.mass, snap0.particles.mass)

snap0.impropers.typeid = [4]
    snap0.impropers.types = ['improperA', 'improperB']
    snap0.impropers.group = [[1, 0, 0, 1]]

    snap0.constraints.N = 1
    snap0.constraints.value = [1.1]
    snap0.constraints.group = [[0, 1]]

    snap0.pairs.N = 1
    snap0.pairs.types = ['pairA', 'pairB']
    snap0.pairs.typeid = [1]
    snap0.pairs.group = [[0, 3]]

    snap0.log['value'] = [1, 2, 4, 10, 12, 18, 22]

    snap1 = gsd.hoomd.Snapshot()
    snap1.particles.N = 2
    snap1.particles.position = [[-2, -1, 0], [1, 3.0, 0.5]]

    snap2 = gsd.hoomd.Snapshot()
    snap2.particles.N = 3
    snap2.particles.types = ['q', 's']
    snap2.particles.type_shapes = \
        [{}, {"type": "Ellipsoid", "a": 7.0, "b": 5.0, "c": 3.0}]
    snap2.bonds.N = 3
    snap2.angles.N = 4
    snap2.dihedrals.N = 5
    snap2.impropers.N = 6
    snap2.constraints.N = 4
    snap2.pairs.N = 7

    with gsd.hoomd.open(name=tmp_path / "test_fallback.gsd",

`Snapshot` with the frame data

        Replace any data chunks not present in the given frame with either data
        from frame 0, or initialize from default values if not in frame 0. Cache
        frame 0 data to avoid file read overhead. Return any default data as
        non-writable numpy arrays.
        """
        if idx >= len(self):
            raise IndexError

        logger.debug('reading frame ' + str(idx) + ' from: ' + str(self.file))

        if self._initial_frame is None and idx != 0:
            self.read_frame(0)

        snap = Snapshot()
        # read configuration first
        if self.file.chunk_exists(frame=idx, name='configuration/step'):
            step_arr = self.file.read_chunk(frame=idx,
                                            name='configuration/step')
            snap.configuration.step = step_arr[0]
        else:
            if self._initial_frame is not None:
                snap.configuration.step = self._initial_frame.configuration.step
            else:
                snap.configuration.step = \
                    snap.configuration._default_value['step']

        if self.file.chunk_exists(frame=idx, name='configuration/dimensions'):
            dimensions_arr = self.file.read_chunk(
                frame=idx, name='configuration/dimensions')
            snap.configuration.dimensions = dimensions_arr[0]