Allow variant_position delta encoding to work with any dtype

Author: tomwhite

sgkit/io/vcf/utils.py

@@ -196,7 +196,7 @@ def get_chunk_size(dim: Hashable, size: int) -> int:
 
         # Position is monotonically increasing (within a contig) so benefits from delta encoding
         if var == "variant_position":
-            default_encoding[var]["filters"] = [Delta(dtype="i4", astype="i4")]
+            default_encoding[var]["filters"] = [Delta(ds[var].dtype)]
 
     return default_encoding