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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 charindex(self, line, column):
 """Gets the absolute character index of the line and column in the continuous string."""

        #Make sure that we have chars and lines to work from if this
        #gets called before linenum() does.
        if len(self._lines) == 0:
            self.linenum(1)

        if line < len(self._chars):
            return self._chars[line - 1] + column
        else:
            return len(self.refstring)