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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 Open(self, path_spec):
 """Opens a volume defined by path specification. Args: path_spec (PathSpec):
 a path specification. Raises: VolumeSystemError: if the TSK partition virtual file system could not be resolved. """

    self._file_system = resolver.Resolver.OpenFileSystem(path_spec)
    if self._file_system is None:
      raise errors.VolumeSystemError('Unable to resolve path specification.')

    type_indicator = self._file_system.type_indicator
    if type_indicator != definitions.TYPE_INDICATOR_TSK_PARTITION:
      raise errors.VolumeSystemError('Unsupported type indicator.')