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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _FormatNotes(self, event):
 """Formats the notes. Args: event (EventObject):
 event. Returns: str: formatted notes field. """

    inode = event.inode
    if inode is None:
      inode = '-'

    notes = getattr(event, 'notes', '')
    if not notes:
      display_name = getattr(event, 'display_name', '')
      notes = 'File: {0:s} inode: {1!s}'.format(display_name, inode)
    return self._SanitizeField(notes)