Add ValidatorRegistryDeltaBlock RLP object

Author: Bhargavasomu

eth/beacon/types/validator_registry_delta_block.py

@@ -0,0 +1,52 @@
+from eth_typing import (
+    Hash32,
+)
+import rlp
+
+from eth.beacon.utils.hash import (
+    hash_eth2,
+)
+from eth.rlp.sedes import (
+    hash32,
+    uint24,
+    uint384,
+    uint64,
+)
+
+
+class ValidatorRegistryDeltaBlock(rlp.Serializable):
+    """
+    Note: using RLP until we have standardized serialization format.
+    """
+    fields = [
+        ('latest_registry_delta_root', hash32),
+        ('validator_index', uint24),
+        ('pubkey', uint384),
+        ('flag', uint64)
+    ]
+
+    def __init__(self,
+                 latest_registry_delta_root: Hash32,
+                 validator_index: int,
+                 pubkey: int,
+                 flag: int) -> None:
+        super().__init__(
+            latest_registry_delta_root=latest_registry_delta_root,
+            validator_index=validator_index,
+            pubkey=pubkey,
+            flag=flag,
+        )
+
+    _hash = None
+
+    @property
+    def hash(self) -> Hash32:
+        if self._hash is None:
+            self._hash = hash_eth2(rlp.encode(self))
+        return self._hash
+
+    @property
+    def root(self) -> Hash32:
+        # Alias of `hash`.
+        # Using flat hash, might change to SSZ tree hash.
+        return self.hash