code: def _validate_index_level(self, level):
          
          if isinstance(level, int):
              if level < 0 and level != -1:
                  raise IndexError("Too many levels: Index has only 1 level,"
                                   " %d is not a valid level number" % (level, ))
              elif level > 0:
                  raise IndexError("Too many levels:"
                                   " Index has only 1 level, not %d" %
                                   (level + 1))
          elif level != self.name:
              raise KeyError('Level %s must be same as name (%s)' %
                             (level, self.name))
docs: Validate index level.
  
          For single-level Index getting level number is a no-op, but some
          verification must be done like in MultiIndex.