Missing hash symbol for comments in prometheus formatter

[Reallife]

Describe the bug

Prometheus formatter doesn't add hash (#) symbol for comments (strings that starts with tokens HELP and TYPE)

Expected behaviour

Prometheus formatter must add hash symbol for comments:

# HELP some metric description

Actual behaviour

Prometheus formatter doesn't add this symbol:

HELP some metric description

Steps to reproduce the behavior:

• Create new metric with description and type
• Format that metric with prometheus formatter
• See the output, for example via /metric endtpoint