code: def get_volume_names(self, volume_file):
          
          out = []
          fp = open(volume_file, 'r')
          for line in fp.readlines():
              if not line.startswith("Volume Name:"):
                  continue
              volname = line[12:-1]
              out.append(volname)
          fp.close()
          return out
docs: Return a dictionary for which key are volume names according to the
          output of gluster volume info stored in volume_file.