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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 _init_alphabet_from_tokens(self, tokens):
 """Initialize alphabet from an iterable of token or subtoken strings."""

        # Include all characters from all tokens in the alphabet to guarantee that
        # any token can be encoded. Additionally, include all escaping
        # characters.
        self._alphabet = {c for token in tokens for c in token}
        self._alphabet |= _ESCAPE_CHARS