Duplicate field PmfGrp.Pmf._25Gps

I get a Error when trying to parse a yang file like below:
grouping pmf-grp {
leaf pmf {
type enumeration {
enum 2.5Gps

{ description "pmf optional"; }

enum 25Gps

{ description "pmf mandatory"; }

enum 100Gps

{ description "undo pmf"; }

}
default 100Gps;
}
}
the error is:
Duplicate field PmfGrp.Pmf._25Gps
Is this a bug in yangtools?