Got started on materialization code for intermediate datasets

These are the steps required to produce the raw dataset referenced here:
https://github.com/bugout-dev/moonstream/issues/272#issuecomment-926087702

Intermediate steps:
https://github.com/bugout-dev/moonstream/issues/272#issuecomment-927144872

datasets/nfts/nfts/cli.py

@@ -0,0 +1,9 @@
+from moonstreamdb.db import yield_db_session_ctx
+
+from .materialize import get_rows, EventType
+
+if __name__ == "__main__":
+    with yield_db_session_ctx() as db_session:
+        rows = get_rows(db_session, EventType.TRANSFER)
+        for row in rows:
+            print(row)

datasets/nfts/nfts/materialize.py

@@ -0,0 +1,66 @@
+from dataclasses import dataclass
+from enum import Enum
+from typing import List, Optional
+
+from moonstreamdb.models import (
+    EthereumAddress,
+    EthereumLabel,
+    EthereumTransaction,
+    EthereumBlock,
+)
+from sqlalchemy.orm import Session
+
+
+@dataclass
+class BlockBounds:
+    starting_block: int
+    ending_block: Optional[int] = None
+
+
+class EventType(Enum):
+    TRANSFER = "nft_transfer"
+    MINT = "nft_mint"
+
+
+@dataclass
+class NFTEvent:
+    event_type: EventType
+    nft_address: str
+    token_id: str
+    from_address: str
+    to_address: str
+    transaction_hash: str
+    value: Optional[int] = None
+    block_number: Optional[int] = None
+    timestamp: Optional[int] = None
+
+
+def get_rows(
+    db_session: Session, event_type: EventType, bounds: Optional[BlockBounds] = None
+) -> List[NFTEvent]:
+    query = (
+        db_session.query(
+            EthereumLabel.label,
+            EthereumAddress.address,
+            EthereumLabel.label_data,
+            EthereumLabel.transaction_hash,
+        )
+        .join(EthereumAddress, EthereumLabel.address_id == EthereumAddress.id)
+        .outerjoin(
+            EthereumTransaction,
+            EthereumLabel.transaction_hash == EthereumTransaction.hash,
+        )
+        .filter(EthereumLabel.label == event_type.value)
+        .limit(10)
+    )
+    return [
+        NFTEvent(
+            event_type=label,
+            nft_address=address,
+            token_id=label_data["tokenId"],
+            from_address=label_data["from"],
+            to_address=label_data["to"],
+            transaction_hash=transaction_hash,
+        )
+        for label, address, label_data, transaction_hash in query
+    ]