code: def check_hex(value):
      
      length = len(value)
      if length not in (3, 6):
          raise ValueError('Hex string #{} is too long'.format(value))
  
      regex = r'[0-9a-f]{{{length}}}'.format(length=length)
      if not re.search(regex, value, re.I):
          raise ValueError('Invalid Hex String: #{}'.format(value))
docs: Check if the given hex value is a valid RGB color
  
      It should match the format: [0-9a-fA-F]
      and be of length 3 or 6.