Hi,
in the Documentation for delta it is written:
delta[a, -b] represents the identity tensor on any vector bundle. In the presence of a metric the object delta[-b, a] is also allowed, being related to the former as given by that metric.
However, the default usage is delta[-b,a] as can be easily checked by introducing a bundle and typing delta[a,-b] which gives an error. It would be nice if that was fixed.
Greetings
Stefan