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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 GetAnalyzerInstance(cls, analyzer_name):
 """Retrieves an instance of a specific analyzer. Args: analyzer_name (str):
 name of the analyzer to retrieve. Returns: BaseAnalyzer: analyzer instance. Raises: KeyError: if analyzer class is not set for the corresponding name. """

    analyzer_name = analyzer_name.lower()
    if analyzer_name not in cls._analyzer_classes:
      raise KeyError(
          'analyzer class not set for name: {0:s}.'.format(analyzer_name))

    analyzer_class = cls._analyzer_classes[analyzer_name]
    return analyzer_class()