Merge pull request #200 from ZQPei/dependabot/pip/pyyaml-5.4

Bump pyyaml from 5.3.1 to 5.4

Author: ZQPei

requirements.txt

@@ -29,7 +29,7 @@ pytest==5.4.1
 pytest-benchmark==3.2.3
 python-dateutil==2.8.1
 pytz==2019.3
-PyYAML==5.3.1
+PyYAML==5.4
 scikit-learn==0.22.2.post1
 scipy==1.4.1
 six==1.14.0