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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 CreatePrecisionHelper(cls, precision):
 """Creates a precision helper. Args: precision (str):
 precision of the date and time value, which should be one of the PRECISION_VALUES in definitions. Returns: class: date time precision helper class. Raises: ValueError: if the precision value is unsupported. """

    precision_helper_class = cls._PRECISION_CLASSES.get(precision, None)
    if not precision_helper_class:
      raise ValueError('Unsupported precision: {0!s}'.format(precision))

    return precision_helper_class