code: def length(value, min=None, max=None):
      
      if (min is not None and min < 0) or (max is not None and max < 0):
          raise AssertionError(
              '`min` and `max` need to be greater than zero.'
          )
      return between(len(value), min=min, max=max)
docs: Return whether or not the length of given string is within a specified
      range.
  
      Examples::
  
          >>> length('something', min=2)
          True
  
          >>> length('something', min=9, max=9)
          True
  
          >>> length('something', max=5)
          ValidationFailure(func=length, ...)
  
      :param value:
          The string to validate.
      :param min:
          The minimum required length of the string. If not provided, minimum
          length will not be checked.
      :param max:
          The maximum length of the string. If not provided, maximum length
          will not be checked.
  
      .. versionadded:: 0.2