Query items based on system call number or name.

def query_item(self, key, abis):
        """Query items based on system call number or name."""
        try:
            key = int(key)
            field = 'number'
        except ValueError:
            try:
                key = int(key, 16)
                field = 'number'
            except ValueError:
                field = 'name'
        arg = and_(getattr(Item, field) == key,
                   or_(Item.abi == abi for abi in abis))
        return self.session.query(Item).filter(arg).all()