update 'get_caf' method signature with better typing

Author: jennifer-bowser

src/anyvlm/functions/get_caf.py

@@ -3,15 +3,21 @@
 from ga4gh.va_spec.base.core import CohortAlleleFrequencyStudyResult
 
 from anyvlm.anyvar.base_client import BaseAnyVarClient
+from anyvlm.utils.types import (
+    ChromosomeName,
+    GenomicSequence,
+    GrcAssemblyId,
+    UscsAssemblyBuild,
+)
 
 
 def get_caf(
     anyvar_client: BaseAnyVarClient,
-    assembly_id: str,
-    reference_name: str,
+    assembly_id: GrcAssemblyId | UscsAssemblyBuild,
+    reference_name: ChromosomeName,
     start: int,
-    reference_bases: str,
-    alternate_bases: str,
+    reference_bases: GenomicSequence,
+    alternate_bases: GenomicSequence,
 ) -> list[CohortAlleleFrequencyStudyResult]:
     """Retrieve Cohort Allele Frequency data for all known variants matching provided search params