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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 set_block_scalar_indent(token_class):
 """Set an explicit indentation level for a block scalar."""

        def callback(lexer, match, context):
            text = match.group()
            context.block_scalar_indent = None
            if not text:
                return
            increment = match.group(1)
            if increment:
                current_indent = max(context.indent, 0)
                increment = int(increment)
                context.block_scalar_indent = current_indent + increment
            if text:
                yield match.start(), token_class, text
                context.pos = match.end()
        return callback