Fix search of instances within a given study

Author: hackermd

requirements_test.txt

@@ -1,4 +1,5 @@
-mypy==0.790
-pytest==6.1.1
-pytest-flake8==1.0.6
+mypy==0.910
+pytest==6.2.4
+pytest-cov==2.12.1
+pytest-flake8==1.0.7
 pytest-localserver==0.5.0