old_contents: #!/usr/bin/python3
  
  import wtforms as wtf
  
  INSTRUMENT_TYPES = [('OISSwap', 'OIS Swap'), ('OISCashRate', 'OIS Cash Rate')]
  
  class Instrument(wtf.Form):
      instrument_type = wtf.SelectField('Instrument', choices=INSTRUMENT_TYPES)
      expiry = wtf.DateField('Expiry', '%Y-%m-%d')
      rate = wtf.DecimalField('Rate')
  
  class InstrumentList(wtf.Form):
      instruments = wtf.FieldList(wtf.FormField(Instrument), min_entries=3)
      submit = wtf.SubmitField()
  
new_contents: #!/usr/bin/python3
  
  import wtforms as wtf
  import wtforms.fields.html5 as wtffields
  
  INSTRUMENT_TYPES = [('OISSwap', 'OIS Swap'), ('OISCashRate', 'OIS Cash Rate')]
  
  class Instrument(wtf.Form):
      instrument_type = wtf.SelectField('Instrument', choices=INSTRUMENT_TYPES)
      expiry = wtffields.DateField('Expiry', '%Y-%m-%d')
      rate = wtffields.DecimalField('Rate')
  
  class InstrumentList(wtf.Form):
      instruments = wtf.FieldList(wtf.FormField(Instrument), min_entries=3)
      submit = wtf.SubmitField()
  
subject: add HTML5 fields