add operation to extract subdict from dict

backend/metagenedb/utils/dict_operations.py

+import logging
+
+logging.basicConfig(level=logging.INFO)
+_LOGGER = logging.getLogger(__name__)
+
+
+def extract_dict(source_dict, keys):
+    """
+    Extract a dict from a given dict based on a given set of keys
+    """
+    extracted_dict = {}
+    for key in keys:
+        try:
+            extracted_dict[key] = source_dict[key]
+            del source_dict[key]
+        except KeyError:
+            _LOGGER.warning(f"[{key}] is not found in the source dict, extraction skipped for this key.")
+    return extracted_dict

backend/metagenedb/utils/test_dict_operations.py

+from unittest import TestCase
+
+from metagenedb.utils.dict_operations import extract_dict
+
+
+class TestExtractDict(TestCase):
+
+    def test_extract_dict(self):
+        source_dict = {'a': 1, 'b': 2}
+        extract_keys = ['b']
+        expected_source_dict = {'a': 1}
+        expected_extract_dict = {'b': 2}
+        test_extract_dict = extract_dict(source_dict, extract_keys)
+        self.assertDictEqual(source_dict, expected_source_dict)
+        self.assertDictEqual(test_extract_dict, expected_extract_dict)
+
+    def test_extract_dict_wrong_key(self):
+        source_dict = {'a': 1, 'b': 2}
+        extract_keys = ['c']
+        expected_source_dict = {'a': 1, 'b': 2}
+        expected_extract_dict = {}
+        test_extract_dict = extract_dict(source_dict, extract_keys)
+        self.assertDictEqual(source_dict, expected_source_dict)
+        self.assertDictEqual(test_extract_dict, expected_extract_dict)