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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 CopyTextToLabel(cls, text, prefix=''):
 """Copies a string to a label. A label only supports a limited set of characters therefore unsupported characters are replaced with an underscore. Args: text (str):
 label text. prefix (Optional[str]):
 label prefix. Returns: str: label. """

    text = '{0:s}{1:s}'.format(prefix, text)
    return cls._INVALID_LABEL_CHARACTERS_REGEX.sub('_', text)