code: def combine_tax_scales(node):
      
      combined_tax_scales = None
      for child_name in node:
          child = node[child_name]
  
          if not isinstance(child, AbstractTaxScale):
              log.info('Skipping {} with value {} because it is not a tax scale'.format(child_name, child))
              continue
  
          if combined_tax_scales is None:
              combined_tax_scales = MarginalRateTaxScale(name = child_name)
              combined_tax_scales.add_bracket(0, 0)
          combined_tax_scales.add_tax_scale(child)
      return combined_tax_scales
docs: Combine all the MarginalRateTaxScales in the node into a single MarginalRateTaxScale.