Returns the group the given @feature and @idx belong to.
f the feature or index do not exist in @pad, -1 is returned.
the feature type to get the group from
the index of the feature to get the group from
The group number of the queried pad feature.
See Implementation
Returns the group the given @feature and @idx belong to.
f the feature or index do not exist in @pad, -1 is returned.