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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 peek(self, size=-1):
 """Return buffered data without advancing the file position. Always returns at least one byte of data, unless at EOF. The exact number of bytes returned is unspecified. """

        self._check_can_read()
        if self._mode == _MODE_READ_EOF or not self._fill_buffer():
            return b""
        return self._buffer