Replace index lookup with first filter.

templates/flags

@@ -1,14 +1,14 @@
 #jinja2: trim_blocks: "false", lstrip_blocks: "true"
 {% for collector in node_exporter_enabled_collectors %}
   {% if not collector is mapping %}
 --collector.{{ collector }} \
   {% else %}
-    {% set name, options = (collector.items()|list)[0] %}
+    {% set name, options = collector.items() | list | first %}
 --collector.{{ name }} \
     {% for k,v in options|dictsort %}
 --collector.{{ name }}.{{ k }}={{ v | quote }} \
     {% endfor %}
   {% endif %}
 {% endfor %}
 {% for collector in node_exporter_disabled_collectors %}
 --no-collector.{{ collector }} \
@@ -17,11 +17,11 @@
 --collector.textfile.directory="{{ node_exporter_textfile_directory }}" \
 {% endif %}
 {% for k,v in node_exporter_extra_flags | dictsort %}
   {% if v == "" %}
 --{{ k }} \
   {% else %}
 --{{ k }}={{ v | quote }} \
   {% endif %}
 {% endfor %}
 --log.level="{{ node_exporter_log_level }}" \
 {% for node_exporter_listen_address in node_exporter_listen_addresses %}