Update Dangerfile

Author: robertodr

Dangerfile

@@ -18,8 +18,5 @@ if git.commits.any? { |c| c.message =~ /^Merge branch '#{github.branch_for_base}
   fail('Please rebase to get rid of the merge commits in this PR')
 end
 
-code_style_validation.check file_extensions: ['.hpp', '.cpp', '.h', '.cc'] 
-
-commit_lint.check
-
-lgtm.check_lgtm
+code_style_validation.check validator: ['yapf'],
+                            file_extensions: ['.py']