feat: Add the is_torrent property to Download objects.

Reference: issue #53.

src/aria2p/downloads.py

@@ -349,6 +349,10 @@ def is_metadata(self):
         """Return True if this download is only composed of metadata, and no actual files."""
         return all(_.is_metadata for _ in self.files)
 
+    @property
+    def is_torrent(self):
+        return "bittorrent" in self._struct
+
     @property
     def total_length(self):
         """Total length of the download in bytes."""

tests/test_downloads.py

@@ -378,6 +378,11 @@ def test_verified_length_string(self):
     def test_verify_integrity_pending(self):
         assert self.download.verify_integrity_pending is None
 
+    def test_is_torrent(self):
+        assert self.download.is_torrent
+        del self.download._struct["bittorrent"]
+        assert not self.download.is_torrent
+
 
 class TestFileClass:
     def setup_method(self):