 (<a class="reference external" href="https://docs.python.org/3/library/stdtypes.html#str" title="(in Python v3.11)"><em>str</em></a><em>, </em><em>optional</em>) – Allows for rotations of a primitive unit cell to be determined from
(hkl) indices specified relative to a conventional unit cell.  Allowed
settings: ‘p’ for primitive (no conversion), ‘f’ for face-centered,
‘i’ for body-centered, and ‘a’, ‘b’, or ‘c’ for side-centered.  Default
behavior is to perform no conversion, i.e.