Example:
sage: CDB=CremonaDatabase()
sage: [[EllipticCurve(ai[0]).label() for ai in C] for C in CDB.isogeny_classes(1728)]
[['1728a1', '1728a2', '1728a3', '1728a4'],
['1728b1'],
['1728ba1'],
['1728bb1', '1728bb2', '1728bb3'],
['1728c1'],
['1728d1'],
['1728e1', '1728e2', '1728e3'],
['1728f1', '1728f2'],
['1728g1'],
['1728h1'],
['1728i1'],
['1728j1', '1728j2', '1728j3'],
['1728k1'],
['1728l1'],
['1728m1', '1728m2'],
['1728n1'],
['1728o1'],
['1728p1'],
['1728q1'],
['1728r1'],
['1728s1', '1728s2', '1728s3'],
['1728t1'],
['1728u1'],
['1728v1', '1728v2', '1728v3', '1728v4'],
['1728w1'],
['1728x1'],
['1728y1'],
['1728z1']]
The keys are strings like '1728a1',...,'1728z1','1728ba1',... and these a wrongly sorted by the standard sort function. What this means is that when iterating through the database, the isogeny classes are not listed in the standard order a,b,...,z,ba,bb,...,bz,...
In the above example, classes ba and bb should come after class z, and not between classes b and c.
