Modify usage

README.md

@@ -84,10 +84,24 @@ First, from the command line install the `datasets` library
 then, from within python load the datasets library.
 
     >>> import datasets
+    >>> from datasets import load_dataset, Features, Value
+
+Specifiy column types to prevent pyarrow error.
+```python
+features = Features({
+    "Type": Value("string"),
+    "DatasetName": Value("string"),
+    "AID": Value("int64"),
+    "ID": Value("string"),
+    "IDType": Value("string"),
+    "SMILES": Value("string")
+})
+```
 
 Now load one of the 'ChAFF' datasets, e.g.,
 
     >>> dataset = datasets.load_dataset("maomlab/ChAFF", name = "default", data_files = "data/Absorbance.csv", split = "train", features = features)
 
+
 You can modify "data/Absorbance.csv" based on your interest (e.g., "data/Reactivity.csv"). 
 The default is split = "train" as we did not split the datasets.