code: def make_header(field_names, permit_not=False):
      
      slug_chars = SLUG_CHARS if not permit_not else SLUG_CHARS + "^"
  
      header = [
          slug(field_name, permitted_chars=slug_chars) for field_name in field_names
      ]
      result = []
      for index, field_name in enumerate(header):
          if not field_name:
              field_name = "field_{}".format(index)
          elif field_name[0].isdigit():
              field_name = "field_{}".format(field_name)
  
          if field_name in result:
              field_name = make_unique_name(
                  name=field_name, existing_names=result, start=2
              )
          result.append(field_name)
  
      return result
docs: Return unique and slugged field names.