<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def find(self, name):
 """Find a vgroup given its name, returning its reference number if found. Args:: name name of the vgroup to find Returns:: vgroup reference number An exception is raised if the vgroup is not found. C library equivalent: Vfind """


        refnum = _C.Vfind(self._hdf_inst._id, name)
        if not refnum:
            raise HDF4Error("vgroup not found")
        return refnum