code: def dollars_to_cents(s, allow_negative=False):
      
      # TODO: Implement cents_to_dollars
      if not s:
          return
  
      if isinstance(s, string_types):
          s = ''.join(RE_NUMBER.findall(s))
  
      dollars = int(round(float(s) * 100))
      if not allow_negative and dollars < 0:
          raise ValueError('Negative values not permitted.')
  
      return dollars
docs: Given a string or integer representing dollars, return an integer of
      equivalent cents, in an input-resilient way.
      
      This works by stripping any non-numeric characters before attempting to
      cast the value.
  
      Examples::
  
          >>> dollars_to_cents('$1')
          100
          >>> dollars_to_cents('1')
          100
          >>> dollars_to_cents(1)
          100
          >>> dollars_to_cents('1e2')
          10000
          >>> dollars_to_cents('-1$', allow_negative=True)
          -100
          >>> dollars_to_cents('1 dollar')
          100