How to find the right function in the Phobos library?

[Bruce]

Example.
I want to find the index of an item in an array.

After a google search and a browse of the Phobos
library, no luck!

Surely D must be an indexOf function that works on
arrays?

Something like...
string[] arr = ["pa", "db", "wb", "ha", "wa"];
int i = arr.indexOf("ha");

I eventually tried ChatGPT and abandoned it after
a number of failed attempts.

So I wrote my own function ...

     size_t indexOf(string[] arr, string key) {
       foreach (size_t i, val; arr)
         if (val == key) return i;
       return -1;
     }

But, this is not satisfying.  The Phobos library should
have this function.

I asked ChatGPT again with my example indexOf and it
came up with countUntil.

auto i = arr.countUntil("ha");

This seems to work but now I'm concerned.
Why was it so hard to find?
What is the best way to search for a function
in the Phobos library?