def get_position_key(atom):
    """
    Get atom position as tuple of integers to be used as lookup key.
    Rounds the coordinates to 4 decimal places before multiplying by 50
    to get unique integer-space coordinates, and avoid floating point errors.

    :param atom: Atom to get key for
    :type atom: :class:`nanome.structure.Atom`
    :return: Position key tuple
    :rtype: (int, int, int)
    """
    return tuple(map(lambda x: int(50 * round(x, 4)), atom.position))