code: def _resolveAddress(address):
          
          address = address.split(':')
          assert len(address) in (1, 2)
          address[0] = socket.gethostbyname(address[0])
          return ':'.join(address)
docs: Resolves the host in the given string. The input is of the form host[:port]. This method
          is idempotent, i.e. the host may already be a dotted IP address.
  
          >>> # noinspection PyProtectedMember
          >>> f=MesosBatchSystem._resolveAddress
          >>> f('localhost')
          '127.0.0.1'
          >>> f('127.0.0.1')
          '127.0.0.1'
          >>> f('localhost:123')
          '127.0.0.1:123'
          >>> f('127.0.0.1:123')
          '127.0.0.1:123'