code: def _rm_udf_link(self, rec):
          '''
          An internal method to remove a UDF File Entry link.
          Parameters:
           rec - The UDF File Entry to remove.
          Returns:
           The number of bytes to remove from the ISO.
          '''
          if not rec.is_file() and not rec.is_symlink():
              raise pycdlibexception.PyCdlibInvalidInput('Cannot remove a directory with rm_hard_link (try rm_directory instead)')
          logical_block_size = self.pvd.logical_block_size()
          num_bytes_to_remove = 0
          if rec.inode is not None:
              found_index = None
              for index, link in enumerate(rec.inode.linked_records):
                  if id(link) == id(rec):
                      found_index = index
                      break
              else:
                  raise pycdlibexception.PyCdlibInternalError('Could not find inode corresponding to record')
              del rec.inode.linked_records[found_index]
              rec.inode.num_udf -= 1
              if not rec.inode.linked_records:
                  found_index = None
                  for index, ino in enumerate(self.inodes):
                      if id(ino) == id(rec.inode):
                          found_index = index
                          break
                  else:
                      raise pycdlibexception.PyCdlibInternalError('Could not find inode corresponding to record')
                  del self.inodes[found_index]
                  num_bytes_to_remove += rec.get_data_length()
              if rec.inode.num_udf == 0:
                  num_bytes_to_remove += logical_block_size
          else:
              num_bytes_to_remove += logical_block_size
          if rec.parent is None:
              raise pycdlibexception.PyCdlibInternalError('Cannot remove a UDF record with no parent')
          if rec.file_ident is None:
              raise pycdlibexception.PyCdlibInternalError('Cannot remove a UDF record with no file identifier')
          return num_bytes_to_remove + self._rm_udf_file_ident(rec.parent, rec.file_ident.fi)