code: def unicodeify(formula):
      
  
      if '.' in formula:
          raise ValueError('No unicode character exists for subscript period.')
  
      subscript_unicode_map = {0: '₀', 1: '₁', 2: '₂', 3: '₃', 4: '₄',
                               5: '₅', 6: '₆', 7: '₇', 8: '₈', 9: '₉'}
  
      for original_subscript, subscript_unicode in subscript_unicode_map.items():
          formula = formula.replace(str(original_subscript), subscript_unicode)
  
      return formula
docs: Generates a formula with unicode subscripts, e.g. Fe2O3 is transformed
      to Fe₂O₃. Does not support formulae with decimal points.
  
      :param formula:
      :return: