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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 sign(self, consumer_secret, method, url, oauth_token_secret=None, **params):
 """Create a signature using PLAINTEXT."""

        key = self._escape(consumer_secret) + b'&'
        if oauth_token_secret:
            key += self._escape(oauth_token_secret)
        return key.decode()