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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 GetHasher(cls, hasher_name):
 """Retrieves an instance of a specific hasher. Args: hasher_name (str):
 the name of the hasher to retrieve. Returns: BaseHasher: hasher. Raises: KeyError: if hasher class is not set for the corresponding name. """

    hasher_name = hasher_name.lower()
    if hasher_name not in cls._hasher_classes:
      raise KeyError(
          'hasher class not set for name: {0:s}.'.format(hasher_name))

    hasher_class = cls._hasher_classes[hasher_name]
    return hasher_class()