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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 visible_line_width(self, position = Point):

 """Return the visible width of the text in line buffer up to position."""

        extra_char_width = len([ None for c in self[:position].line_buffer if 0x2013 <= ord(c) <= 0xFFFD])
        return len(self[:position].quoted_text()) + self[:position].line_buffer.count(u"\t")*7 + extra_char_width