add irradiance.dni() function to Decomposing and combining irradiance section of api.rst. this seems to be the most reasonable section to reference the function. Issue pvlib#686.

tahentx · tahentx · commit f4af87116b9b · 2019-04-23T17:17:07.000-07:00
diff --git a/docs/sphinx/source/api.rst b/docs/sphinx/source/api.rst
@@ -153,6 +153,7 @@ Decomposing and combining irradiance
    irradiance.beam_component
    irradiance.poa_components
    irradiance.get_ground_diffuse
+   irradiance.dni
 
 Transposition models
 --------------------
