Add instructions to convert ORD data to JSON object (open-reaction-da…

…tabase#179)

* Add instructions to convert ORD data to JSON object

* Relocate the section position

README.md

@@ -10,6 +10,59 @@ We use [Git LFS](https://git-lfs.github.com) to efficiently store
 the Dataset records that make up the ORD. To view these files locally, you'll
 need to install Git LFS before cloning the repository.
 
+## Data Manipulation
+
+The `ord-data` repository contains the Open Reaction Database (ORD) in Google's Protobuf binary
+format, which is stored in the [`data`](data) directory. Currently, all the data are stored in e.g.
+*.pb.gz format (compressed Protobuf binary files) for the sake of efficiency. The user can convert
+the data into human readable text format, *.pb.txt.
+
+```python
+# import requirements
+from ord_schema.message_helpers import load_message, write_message
+from ord_schema.proto import dataset_pb2
+
+# load the binary ord file
+dataset = load_message("input_fname.pb.gz", dataset_pb2.Dataset)
+# save the ord file as human readable text
+write_message(dataset, "output_fname.pbtxt")
+```
+
+We can also convert ORD data into JSON format.
+
+```python
+# import requirements
+import json
+
+from ord_schema.message_helpers import load_message, write_message
+from ord_schema.proto import dataset_pb2
+from google.protobuf.json_format import MessageToJson
+
+input_fname = "sample_file.pb.gz"
+dataset = load_message(
+    input_fname,
+    dataset_pb2.Dataset,
+)
+
+# take one reaction message from the dataset for example
+rxn = dataset.reactions[0]
+rxn_json = json.loads(
+    MessageToJson(
+        message=rxn,
+        including_default_value_fields=False,
+        preserving_proto_field_name=True,
+        indent=2,
+        sort_keys=False,
+        use_integers_for_enums=False,
+        descriptor_pool=None,
+        float_precision=None,
+        ensure_ascii=True,
+    )
+)
+
+print(f"We have converted the {input_fname} to JSON format shown as below, \n{rxn_json}")
+```
+
 ## Contributing
 
 Please see the [Submission Workflow](https://docs.open-reaction-database.org/en/latest/submissions.html) documentation. Make sure to review the [license](https://github.com/open-reaction-database/ord-data/blob/main/LICENSE) and [terms of use](https://github.com/open-reaction-database/ord-data/blob/main/CONTRIBUTING.md#terms-of-use).