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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 _fill_text(self, text, width=None, indent=None):
 """ Reflow text width while maintaining certain formatting characteristics like double newlines and indented statements. """

        assert isinstance(text, str)
        if indent is None:
            indent = NBSP * self._current_indent
        assert isinstance(indent, str)
        paragraphs = []
        line_buf = []
        pre = ''
        for fragment in text.splitlines():
            pre_indent = self.leadingws.match(fragment)
            if not fragment or pre_indent:
                if line_buf:
                    line = ' '.join(line_buf)
                    paragraphs.append((pre, self.whitespace.sub(' ', line)))
                if not fragment:
                    paragraphs.append(('', ''))
                else:
                    pre = pre_indent.group()
                    fragment = self.leadingws.sub('', fragment)
                    paragraphs.append((pre, fragment))
                line_buf = []
                pre = ''
            else:
                line_buf.append(fragment)
        if line_buf:
            line = ' '.join(line_buf)
            paragraphs.append((pre, self.whitespace.sub(' ', line)))
        indent = VTMLBuffer(indent)
        nl = VTMLBuffer('\n')
        if width is None:
            width = self._width - len(indent)
        lines = []
        for pre, paragraph in paragraphs:
            pwidth = width - len(pre)
            lines.append(nl.join((indent + pre + x)
                         for x in vtmlrender(paragraph).wrap(pwidth)))
        return nl.join(lines)