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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 main(self, main):
 """Specifies a Main-Class entry for this jar's manifest. :param string main: a fully qualified class name """

    if not main or not isinstance(main, string_types):
      raise ValueError('The main entry must be a non-empty string')
    self._main = main