fix: assert on single element of basepath list rather than whole list

Author: reedham-aws

samtranslator/model/api/api_generator.py

@@ -559,7 +559,7 @@ def _construct_api_domain(  # noqa: PLR0912, PLR0915
                     mapping_basepath = basepath
                     logical_id = self.logical_id + "BasePathMapping"
                 else:
-                    sam_expect(basepaths, self.logical_id, "Domain.BasePath").to_be_a_list_of(ExpectedType.STRING)
+                    sam_expect(basepath, self.logical_id, "Domain.BasePath").to_be_a_list_of(ExpectedType.STRING)
                     # Remove possible leading and trailing '/' because a base path may only
                     # contain letters, numbers, and one of "$-_.+!*'()"
                     path = "".join(e for e in basepath if e.isalnum())