'Simple check to see if VG exists.
:returns: True if vg specified in object exists, else False'

def _vg_exists(self):

    exists = False
    cmd = (LVM.LVM_CMD_PREFIX + ['vgs', '--noheadings', '-o', 'name', self.vg_name])
    (out, _err) = self._execute(root_helper=self._root_helper, run_as_root=True, *cmd)
    if (out is not None):
        volume_groups = out.split()
        if (self.vg_name in volume_groups):
            exists = True
    return exists
