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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 passthrough_proc(self, inputstring, **kwargs):
 """Process python passthroughs."""

        out = []
        found = None  # store of characters that might be the start of a passthrough
        hold = None  # the contents of the passthrough so far
        count = None  # current parenthetical level (num closes - num opens)
        multiline = None  # if in a passthrough, is it a multiline passthrough
        skips = self.copy_skips()

        for i, c in enumerate(append_it(inputstring, "\n")):
            if hold is not None:
                # we specify that we only care about parens, not brackets or braces
                count += paren_change(c, opens="(", closes=")")
                if count >= 0 and c == hold:
                    out.append(self.wrap_passthrough(found, multiline))
                    found = None
                    hold = None
                    count = None
                    multiline = None
                else:
                    if c == "\n":
                        skips = addskip(skips, self.adjust(lineno(i, inputstring)))
                    found += c
            elif found:
                if c == "\\":
                    found = ""
                    hold = "\n"
                    count = 0
                    multiline = False
                elif c == "(":
                    found = ""
                    hold = ")"
                    count = -1
                    multiline = True
                else:
                    out.append("\\" + c)
                    found = None
            elif c == "\\":
                found = True
            else:
                out.append(c)

        if hold is not None or found is not None:
            raise self.make_err(CoconutSyntaxError, "unclosed passthrough", inputstring, i)

        self.set_skips(skips)
        return "".join(out)