Prometheus.PlugPipelineInstrumenter generates dialyzer warnings

[Stratus3D]

I've defined a module in our code that uses the PlugPipelineInstrumenter:

  use Prometheus.PlugPipelineInstrumenter

But when I run dialyzer I get the following output for it:

[omitted]/pipeline_instrumenter.ex:4: The inferred type for the 1st argument of call/2 (#{'__struct__':='Elixir.Plug.Conn', 'adapter':={atom(),_}, 'assigns':=#{atom()=>_}, 'before_send':=[fun((_) -> any())], 'body_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [any()] | map()}, 'cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'halted':=_, 'host':=binary(), 'method':=binary(), 'owner':=pid(), 'params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [any()] | map()}, 'path_info':=[binary()], 'path_params':=#{binary()=>binary() | [any()] | map()}, 'port':=char(), 'private':=#{atom()=>_}, 'query_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [any()] | map()}, 'query_string':=binary(), 'remote_ip':={byte(),byte(),byte(),byte()} | {char(),char(),char(),char(),char(),char(),char(),char()}, 'req_cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'req_headers':=[{_,_}], 'request_path':=binary(), 'resp_body':='nil' | binary() | maybe_improper_list(binary() | maybe_improper_list(any(),binary() | []) | byte(),binary() | []), 'resp_cookies':=#{binary()=>map()}, 'resp_headers':=[{_,_}], 'scheme':='http' | 'https', 'script_name':=[binary()], 'secret_key_base':='nil' | binary(), 'state':='chunked' | 'file' | 'sent' | 'set' | 'set_chunked' | 'set_file' | 'unset', 'status':='nil' | non_neg_integer()}) is not a supertype of #{'__struct__':='Elixir.Plug.Conn', 'adapter':={atom(),_}, 'assigns':=#{atom()=>_}, 'before_send':=[fun((#{'__struct__':='Elixir.Plug.Conn', 'adapter':={_,_}, 'assigns':=map(), 'before_send':=[fun((_) -> any())], _=>_}) -> #{'__struct__':='Elixir.Plug.Conn', 'adapter':={_,_}, 'assigns':=map(), 'before_send':=[fun((_) -> any())], _=>_})], 'body_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | #{binary()=>_}] | #{binary()=>binary() | [any()] | #{binary()=>_}}}, 'cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'halted':=_, 'host':=binary(), 'method':=binary(), 'owner':=pid(), 'params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | #{binary()=>_}] | #{binary()=>binary() | [any()] | #{binary()=>_}}}, 'path_info':=[binary()], 'path_params':=#{binary()=>binary() | [binary() | [any()] | #{binary()=>_}] | #{binary()=>binary() | [any()] | #{binary()=>_}}}, 'peer':={{byte(),byte(),byte(),byte()} | {char(),char(),char(),char(),char(),char(),char(),char()},char()}, 'port':=char(), 'private':=#{atom()=>_}, 'query_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | #{binary()=>_}] | #{binary()=>binary() | [any()] | #{binary()=>_}}}, 'query_string':=binary(), 'remote_ip':={byte(),byte(),byte(),byte()} | {char(),char(),char(),char(),char(),char(),char(),char()}, 'req_cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'req_headers':=[{binary(),binary()}], 'request_path':=binary(), 'resp_body':='nil' | binary() | maybe_improper_list(binary() | maybe_improper_list(any(),binary() | []) | byte(),binary() | []), 'resp_cookies':=#{binary()=>#{}}, 'resp_headers':=[{binary(),binary()}], 'scheme':='http' | 'https', 'script_name':=[binary()], 'secret_key_base':='nil' | binary(), 'state':='chunked' | 'file' | 'sent' | 'set' | 'set_chunked' | 'set_file' | 'unset', 'status':='nil' | non_neg_integer()}, which is expected type for this argument in the callback of the 'Elixir.Plug' behaviour
[omitted]/pipeline_instrumenter.ex:4: The inferred return type of call/2 (#{'__struct__':='Elixir.Plug.Conn', 'adapter':={atom(),_}, 'assigns':=#{atom()=>_}, 'before_send':=[fun((_) -> any()),...], 'body_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [any()] | map()}, 'cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'halted':=_, 'host':=binary(), 'method':=binary(), 'owner':=pid(), 'params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [any()] | map()}, 'path_info':=[binary()], 'path_params':=#{binary()=>binary() | [any()] | map()}, 'port':=char(), 'private':=#{atom()=>_}, 'query_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [any()] | map()}, 'query_string':=binary(), 'remote_ip':={byte(),byte(),byte(),byte()} | {char(),char(),char(),char(),char(),char(),char(),char()}, 'req_cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'req_headers':=[{_,_}], 'request_path':=binary(), 'resp_body':='nil' | binary() | maybe_improper_list(binary() | maybe_improper_list(any(),binary() | []) | byte(),binary() | []), 'resp_cookies':=#{binary()=>map()}, 'resp_headers':=[{_,_}], 'scheme':='http' | 'https', 'script_name':=[binary()], 'secret_key_base':='nil' | binary(), 'state':='chunked' | 'file' | 'sent' | 'set' | 'set_chunked' | 'set_file' | 'unset', 'status':='nil' | non_neg_integer()}) has nothing in common with #{'__struct__':='Elixir.Plug.Conn', 'adapter':={atom(),_}, 'assigns':=#{atom()=>_}, 'before_send':=[fun((#{'__struct__':='Elixir.Plug.Conn', 'adapter':={_,_}, 'assigns':=map(), 'before_send':=[fun((_) -> any())], _=>_}) -> #{'__struct__':='Elixir.Plug.Conn', 'adapter':={_,_}, 'assigns':=map(), 'before_send':=[fun((_) -> any())], _=>_})], 'body_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | #{binary()=>_}] | #{binary()=>binary() | [any()] | #{binary()=>_}}}, 'cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'halted':=_, 'host':=binary(), 'method':=binary(), 'owner':=pid(), 'params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | #{binary()=>_}] | #{binary()=>binary() | [any()] | #{binary()=>_}}}, 'path_info':=[binary()], 'path_params':=#{binary()=>binary() | [binary() | [any()] | #{binary()=>_}] | #{binary()=>binary() | [any()] | #{binary()=>_}}}, 'peer':={{byte(),byte(),byte(),byte()} | {char(),char(),char(),char(),char(),char(),char(),char()},char()}, 'port':=char(), 'private':=#{atom()=>_}, 'query_params':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary() | [binary() | [any()] | #{binary()=>_}] | #{binary()=>binary() | [any()] | #{binary()=>_}}}, 'query_string':=binary(), 'remote_ip':={byte(),byte(),byte(),byte()} | {char(),char(),char(),char(),char(),char(),char(),char()}, 'req_cookies':=#{'__struct__'=>'Elixir.Plug.Conn.Unfetched', 'aspect'=>atom(), binary()=>binary()}, 'req_headers':=[{binary(),binary()}], 'request_path':=binary(), 'resp_body':='nil' | binary() | maybe_improper_list(binary() | maybe_improper_list(any(),binary() | []) | byte(),binary() | []), 'resp_cookies':=#{binary()=>#{}}, 'resp_headers':=[{binary(),binary()}], 'scheme':='http' | 'https', 'script_name':=[binary()], 'secret_key_base':='nil' | binary(), 'state':='chunked' | 'file' | 'sent' | 'set' | 'set_chunked' | 'set_file' | 'unset', 'status':='nil' | non_neg_integer()}, which is the expected return type for the callback of the 'Elixir.Plug' behaviour

Any idea what the cause of this is? And is there any way I can fix this by making changes to my own source code?

Thanks!