Merge pull request #285 from azaichen/main

Bug with pandas pivot fixed

Author: avmarchenko

exatomic/core/orbital.py

@@ -384,7 +384,7 @@ def square(self, frame=0, column='coef', mocoefs=None, irrep=None):
                 nchi = (irreps.chi.max() + 1).sum()
                 cmat = np.zeros((nchi, norb))
                 for irrep, grp in irreps:
-                    piv = grp.pivot('chi', 'orbital', mocoefs)
+                    piv = grp.pivot_table(index='chi', columns='orbital', values=mocoefs)
                     ii, jj = piv.shape
                     cmat[i : i + ii, j : j + jj] = piv.values
                     i += ii