add auto record example

examples/basic/auto_record.py

@@ -0,0 +1,30 @@
+import pandas as pd
+import rltk
+
+print('from dataframe...')
+
+df = pd.read_csv('ds1.csv', encoding='latin-1')
+df['id'] = df['doc_id'].astype('str')
+
+
+class DFRecord(rltk.AutoGeneratedRecord):
+    pass
+
+
+ds = rltk.Dataset(rltk.DataFrameReader(df), record_class=DFRecord)
+for r in ds:
+    print(r.id, r.doc_id, r.doc_value)
+
+
+print('set id column...')
+
+
+@rltk.set_id('col1', function_=lambda x: str(x), keep_original=True)
+class DFRecord2(rltk.AutoGeneratedRecord):
+    pass
+
+
+df = pd.DataFrame({'col1': [1, 2], 'col2': [3, 4]})
+ds = rltk.Dataset(reader=rltk.DataFrameReader(df), record_class=DFRecord2)
+for r in ds:
+    print(r.id, r.col1, r.col2)