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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 _enter_newline(self):
 """ Remove the trailing spaces in the current line, and then mark that the leading spaces of the next line need to be removed. .. seealso:: `CSS Text Module Level 3 - The White Space Processing Rules <http://www.w3.org/TR/css3-text/#white-space-phase-2>`_ """


        last_text_idx = self._last_text_idx
        if last_text_idx >= 0:
            buf = self._buffer
            buf[last_text_idx] = buf[last_text_idx].rstrip()

        self._remove_begining_ws = True