code: def add_pv(self, device):
          
          if not os.path.exists(device):
              raise ValueError("%s does not exist." % device)
          self.open()
          ext = lvm_vg_extend(self.handle, device)
          if ext != 0:
              self.close()
              raise CommitError("Failed to extend Volume Group.")
          self._commit()
          self.close()
          return PhysicalVolume(self, name=device)
docs: Initializes a device as a physical volume and adds it to the volume group::
  
              from lvm2py import *
  
              lvm = LVM()
              vg = lvm.get_vg("myvg", "w")
              vg.add_pv("/dev/sdbX")
  
          *Args:*
  
          *       device (str):   An existing device.
  
          *Raises:*
  
          *       ValueError, CommitError, HandleError
  
         .. note::
  
              The VolumeGroup instance must be in write mode, otherwise CommitError
              is raised.