`iotbx.explore_metric_symmetry` is a program that allows a user to quickly
determine the symmetry of the lattice, given a unit cell, and determine
relations between various possible point groups.

Another use of `iotbx.explore_metric_symmetry` is in the comparison of
related unit cells, that are related by a linear recombination of their basis
vectors.

A list of keywords and concise help can be obtained by typing: `iotbx.explore_metric_symmetry`

options: -h, --help show this help message and exit --unit_cell=10,10,20,90,90,120|FILENAME External unit cell parameters --space_group=P212121|FILENAME External space group symbol --symmetry=FILENAME External file with symmetry information --max_delta=FLOAT Maximum delta/obliquity used in determining the lattice symmetry, using a modified Le-Page algorithm. Default is 5.0 degrees --start_from_p1 Reduce to Niggli cell and forget the input space group before higher metric symmetry is sought. --graph=GRAPH A graphical representation of the graph will be written out. Requires Graphviz to be installed and in path. --centring_type=CENTRING_TYPE Centring type, choose from P,A,B,C,I,R,F --other_unit_cell=10,20,30,90,103.7,90 Other unit cell, for unit cell comparison --other_space_group=OTHER_SPACE_GROUP space group for other_unit_cell, for unit cell comparison --other_centring_type=OTHER_CENTRING_TYPE Centring type, choose from P,A,B,C,I,R,F --no_point_group_graph Do not carry out the construction of a point group graph. --relative_length_tolerance=FLOAT Tolerance for unit cell lengths to be considered equal-ish. --absolute_angle_tolerance=FLOAT Angular tolerance in unit cell comparison --max_order=INT Maximum volume change for target cell Explore Metric Symmetry. A list of possible unit cells and space groups is given for the given specified unit cell and space group combination.

The keywords `unit_cell`, `space_group` (or `centring_type`) define the
crystal symmetry for which a point group graph is constructed.

The keyword `max_delta` sets the tolerance used the in determination of the lattice
symmetry.

the keyword `start_from_p1` in combination with the space group is equivalent
to specification of the `centring_type` only.

If graphviz is installed, an a png file with the point group graph can be
constructed by specifying the filename of the png graph with the keyword
`graph`.

If a second crystal is specified by the keywords `other_unit_cell`,
`other_space_group` (or `other_centring_type`) the unit cells will be
compared. Using linear combinations of the smallest unit cell, possible
matches for the large unit cell are sought.
If desired, the larger unit cell can be expanded as well using the keyword
`max_order`.

The tolerances in the unit cell comparison can be changed form their defaults
(10% on the lengths and 20 degrees on the angles)
using the keywords `relative_length_tolerance` and `absolute_angle_tolerance`.

Construction of a point group graph can be skipped using the key
`no_point_group_graph`.

Constructing a point group graph given some basic information:

iotbx.explore_metric_symmetry --unit_cell="20,30,40,90,90,90" \ --centring_type=P

All point groups between `P 1` and `P 2 2 2` will be listed

Comparing two related unit cells can be done using:

iotbx.explore_metric_symmetry --unit_cell="20,30,40,90,90,90" \ --centring_type=P --other_unit_cell="40,80,60,90,90,90" \ --other_centring_type=F