Remove raw_dict methods from ArrayStore (#575)

## Description

<!-- Provide a brief description of the PR's purpose here. -->

These methods have never been used outside of the ArrayStore tests.
Furthermore, they introduce unnecessary complexity as part of
implementing the Array API in #571 (it becomes tricky to consider `xp`
and the `device`, in particular).

## TODO

<!-- Notable points that this PR has either accomplished or will
accomplish. -->

- [x] Remove implementation
- [x] Remove tests

## Status

- [x] I have read the guidelines in

[CONTRIBUTING.md](https://github.com/icaros-usc/pyribs/blob/master/CONTRIBUTING.md)
- [x] I have formatted my code using `yapf`
- [x] I have tested my code by running `pytest`
- [x] I have linted my code with `pylint`
- [x] I have added a one-line description of my change to the changelog
in
      `HISTORY.md`
- [x] This PR is ready to go

Author: btjanaka

HISTORY.md

@@ -7,6 +7,8 @@
 #### API
 
 - Support array backends via Python array API Standard ({pr}`573`)
+- **Backwards-incompatible:** Remove raw_dict methods from ArrayStore
+  ({pr}`575`)
 
 ## 0.8.1
 

ribs/archives/_array_store.py

@@ -523,64 +523,3 @@ def resize(self, capacity):
             new_shape = (capacity,) + cur_arr.shape[1:]
             self._fields[name] = np.empty(new_shape, cur_arr.dtype)
             self._fields[name][:cur_capacity] = cur_arr
-
-    def as_raw_dict(self):
-        """Returns the raw data in the ArrayStore as a one-level dictionary.
-
-        To collapse the dict, we prefix each key with ``props.`` or ``fields.``,
-        so the result looks as follows::
-
-            {
-              "props.capacity": ...,
-              "props.occupied": ...,
-              ...
-              "fields.objective": ...,
-              ...
-            }
-
-        Returns:
-            dict: See description above.
-        """
-        d = {}
-        for prefix, attr in [("props", self._props), ("fields", self._fields)]:
-            for name, val in attr.items():
-                if isinstance(val, np.ndarray):
-                    val = readonly(val.view())
-                d[f"{prefix}.{name}"] = val
-        return d
-
-    @staticmethod
-    def from_raw_dict(d):
-        """Loads an ArrayStore from a dict of raw info.
-
-        Args:
-            d (dict): Dict returned by :meth:`as_raw_dict`.
-        Returns:
-            ArrayStore: The new ArrayStore created from d.
-        Raises:
-            ValueError: The loaded props dict has the wrong keys.
-        """
-        # pylint: disable = protected-access
-
-        store = ArrayStore({}, 0)  # Create an empty store.
-
-        props = {
-            name[len("props."):]: arr
-            for name, arr in d.items()
-            if name.startswith("props.")
-        }
-        if props.keys() != store._props.keys():
-            raise ValueError(
-                f"Expected props to have keys {store._props.keys()} but "
-                f"only found {props.keys()}")
-
-        fields = {
-            name[len("fields."):]: arr
-            for name, arr in d.items()
-            if name.startswith("fields.")
-        }
-
-        store._props = props
-        store._fields = fields
-
-        return store

tests/archives/array_store_test.py

@@ -364,71 +364,6 @@ def test_resize_to_double_capacity(store):
     assert np.all(store._fields["objective"][[3, 5]] == [1.0, 2.0])
 
 
-def test_as_raw_dict(store):
-    store.add(
-        [3, 5],
-        {
-            "objective": [1.0, 2.0],
-            "measures": [[1.0, 2.0], [3.0, 4.0]],
-            "solution": [np.zeros(10), np.ones(10)],
-        },
-    )
-
-    d = store.as_raw_dict()
-
-    assert d.keys() == set([
-        "props.capacity",
-        "props.occupied",
-        "props.n_occupied",
-        "props.occupied_list",
-        "props.updates",
-        "fields.objective",
-        "fields.measures",
-        "fields.solution",
-    ])
-    assert d["props.capacity"] == 10
-    assert np.all(d["props.occupied"] == [0, 0, 0, 1, 0, 1, 0, 0, 0, 0])
-    assert d["props.n_occupied"] == 2
-    assert np.all(np.sort(d["props.occupied_list"][:2]) == [3, 5])
-    assert np.all(d["props.updates"] == [1, 0])  # 1 add, 0 clear.
-    assert np.all(d["fields.objective"][[3, 5]] == [1.0, 2.0])
-    assert np.all(d["fields.measures"][[3, 5]] == [[1.0, 2.0], [3.0, 4.0]])
-    assert np.all(d["fields.solution"][[3, 5]] == [np.zeros(10), np.ones(10)])
-
-
-def test_from_raw_dict_invalid_props(store):
-    d = store.as_raw_dict()
-    del d["props.capacity"]
-    with pytest.raises(ValueError):
-        ArrayStore.from_raw_dict(d)
-
-
-def test_from_raw_dict(store):
-    store.add(
-        [3, 5],
-        {
-            "objective": [1.0, 2.0],
-            "measures": [[1.0, 2.0], [3.0, 4.0]],
-            "solution": [np.zeros(10), np.ones(10)],
-        },
-    )
-
-    new_store = ArrayStore.from_raw_dict(store.as_raw_dict())
-
-    assert len(new_store) == 2
-    assert np.all(new_store.occupied == [0, 0, 0, 1, 0, 1, 0, 0, 0, 0])
-    assert np.all(np.sort(new_store.occupied_list) == [3, 5])
-
-    occupied, data = new_store.retrieve([5, 3])
-
-    assert np.all(occupied == [True, True])
-    assert data.keys() == set(["objective", "measures", "solution", "index"])
-    assert np.all(data["objective"] == [2.0, 1.0])
-    assert np.all(data["measures"] == [[3.0, 4.0], [1.0, 2.0]])
-    assert np.all(data["solution"] == [np.ones(10), np.zeros(10)])
-    assert np.all(data["index"] == [5, 3])
-
-
 def test_data(store):
     store.add(
         [3, 5],