Several methods in the Ag3 class, including snp_sites(), site_filters(), snp_genotypes() and snp_dataset() take a contig argument and return values for a whole contig.

Proposed to deprecate the contig argument and replace with a more generalised region argument which could be any of the following:

• A contig (e.g., "3L")
• A contig region (e.g., "3L:1000000-2000000")
• A gene (e.g., "AGAP004070")
• A list/tuple of any of the above, in which case regions get concatenated

Internally this would require support for locating the indices bounding a region.