Add script to look up doc text from qrels for MS MARCO passage (#498)

scripts/msmarco-passage/lookup_docs_from_qrels.py

@@ -0,0 +1,23 @@
+import argparse
+import json
+import sys
+
+# We're going to explicitly use a local installation of Pyserini (as opposed to a pip-installed one).
+# Comment these lines out to use a pip-installed one instead.
+sys.path.insert(0, './')
+
+from pyserini.search import SimpleSearcher
+
+
+if __name__ == '__main__':
+    parser = argparse.ArgumentParser()
+    parser.add_argument('--qrels', type=str, help='qrels file', required=True)
+    parser.add_argument('--index', type=str, help='index location', required=True)
+    args = parser.parse_args()
+
+    searcher = SimpleSearcher(args.index)
+    with open(args.qrels, 'r') as reader:
+        for line in reader.readlines():
+            arr = line.split('\t')
+            doc = json.loads(searcher.doc(arr[2]).raw())['contents']
+            print(f'{arr[2]}\t{doc}')