def Refresh():
    """looks up symbols within the inferior and caches their names / values.

    If debugging information is only partial, this method does its best to
    find as much information as it can, validation can be done using
    IsSymbolFileSane.
    """
    try:
      GdbCache.DICT = gdb.lookup_type('PyDictObject').pointer()
      GdbCache.TYPE = gdb.lookup_type('PyTypeObject').pointer()
    except gdb.error as err:
      # The symbol file we're using doesn't seem to provide type information.
      pass
    interp_head_name = GdbCache.FuzzySymbolLookup('interp_head')
    if interp_head_name:
      GdbCache.INTERP_HEAD = gdb.parse_and_eval(interp_head_name)
    else:
      # As a last resort, ask the inferior about it.
      GdbCache.INTERP_HEAD = gdb.parse_and_eval('PyInterpreterState_Head()')
    GdbCache.PENDINGBUSY = GdbCache.FuzzySymbolLookup('pendingbusy')
    GdbCache.PENDINGCALLS_TO_DO = GdbCache.FuzzySymbolLookup('pendingcalls_to_do')
looks up symbols within the inferior and caches their names / values.

    If debugging information is only partial, this method does its best to
    find as much information as it can, validation can be done using
    IsSymbolFileSane.