0.5.7

• new functions for working with Structure: assign_serial_numbers(), assign_cis_flags(), has_hydrogen()
• enhanced transform_to_assembly()
• functions count_atom_sites() and count_occupancies() now take Selection as an optional arg
• deprecated count_hydrogen_sites(): can be replaced with has_hydrogen() or count_atom_sites(Selection("[H,D]"))
• selection syntax extended with ";polymer" and ";solvent" (it can also be "!polymer,solvent")
• improved preparation of the intermediate file (crd) for Refmac
• gemmi program: several options were added to subprograms
• Ccp4.setup() now returns void (previously – number)
• python: cif.Block.find_pair() and Item.pair were changed to return tuple (previously – list)