Document the `backend` parameter to `pyhmmer.hmmer` functions

src/pyhmmer/hmmer/_hmmscan.py

@@ -129,6 +129,9 @@ def hmmscan(
         background (`pyhmmer.plan7.Background`, *optional*): A background
             object to use for configuring the profiles. If `None` given,
             create a default one.
+        backend (`str`): The parallel backend to use for workers to be
+            executed. Supports ``threading`` to use thread-based parallelism,
+            or ``multiprocessing`` to use process-based parallelism.
 
     Yields:
         `~pyhmmer.plan7.TopHits`: An object reporting *top hits* for each

src/pyhmmer/hmmer/_hmmsearch.py

@@ -135,6 +135,9 @@ def hmmsearch(
         callback (callable): A callback that is called everytime a query is
             processed with two arguments: the query, and the total number
             of queries. This can be used to display progress in UI.
+        backend (`str`): The parallel backend to use for workers to be
+            executed. Supports ``threading`` to use thread-based parallelism,
+            or ``multiprocessing`` to use process-based parallelism.
 
     Yields:
         `~pyhmmer.plan7.TopHits`: An object reporting *top hits* for each
@@ -154,6 +157,9 @@ def hmmsearch(
             >>> hits[0].score
             8.601...
 
+        Since *version 0.11.0*, ``mypy`` should be able to detection which
+        keywords can be passed to `hmmsearch` using a `TypedDict` annotation.
+
     .. versionadded:: 0.1.0
 
     .. versionchanged:: 0.4.9

src/pyhmmer/hmmer/_jackhmmer.py

@@ -306,7 +306,7 @@ def jackhmmer(
         builder (`~pyhmmer.plan7.Builder`, optional): A builder to configure
             how the queries are converted to HMMs. Passing `None` will create
             a default instance.
-        backend (`str`): The parallel backend to use for workers to be 
+        backend (`str`): The parallel backend to use for workers to be
             executed. Supports ``threading`` to use thread-based parallelism,
             or ``multiprocessing`` to use process-based parallelism.
 

src/pyhmmer/hmmer/_nhmmer.py

@@ -162,6 +162,9 @@ def nhmmer(
         builder (`~pyhmmer.plan7.Builder`, optional): A builder to configure
             how the queries are converted to HMMs. Passing `None` will create
             a default instance.
+        backend (`str`): The parallel backend to use for workers to be
+            executed. Supports ``threading`` to use thread-based parallelism,
+            or ``multiprocessing`` to use process-based parallelism.
 
     Yields:
         `~pyhmmer.plan7.TopHits`: A *top hits* instance for each query,

src/pyhmmer/hmmer/_phmmer.py

@@ -128,6 +128,9 @@ def phmmer(
         builder (`~pyhmmer.plan7.Builder`, optional): A builder to configure
             how the queries are converted to HMMs. Passing `None` will create
             a default instance.
+        backend (`str`): The parallel backend to use for workers to be
+            executed. Supports ``threading`` to use thread-based parallelism,
+            or ``multiprocessing`` to use process-based parallelism.
 
     Yields:
         `~pyhmmer.plan7.TopHits`: A *top hits* instance for each query,