Why does this `_headers` not seem to override the content-type header? ``` /favicon.ico Content-T

Why does this

_headers

_headers

_headers

_headers not seem to override the content-type header?

/favicon.ico
  Content-Type: image/png

/favicon.ico
  Content-Type: image/png

/favicon.ico
  Content-Type: image/png

/favicon.ico
  Content-Type: image/png