code: def interpret_bits_value(val):
      
      if isinstance(val, int) or val is None:
          return val
  
      else:
          val = str(val).strip()
  
          if val.startswith('~'):
              flip_bits = True
              val = val[1:].lstrip()
          else:
              flip_bits = False
  
          if val.startswith('('):
              if val.endswith(')'):
                  val = val[1:-1].strip()
              else:
                  raise ValueError('Unbalanced parantheses or incorrect syntax.')
  
          if ',' in val:
              valspl = val.split(',')
              bitmask = 0
              for v in valspl:
                  bitmask += int(v)
  
          elif '+' in val:
              valspl = val.split('+')
              bitmask = 0
              for v in valspl:
                  bitmask += int(v)
  
          elif val.upper() in ['', 'NONE', 'INDEF']:
              return None
  
          else:
              bitmask = int(val)
  
          if flip_bits:
              bitmask = ~bitmask
  
      return bitmask
docs: Converts input bits value from string to a single integer value or None.
      If a comma- or '+'-separated set of values are provided, they are summed.
  
      .. note::
          In order to flip the bits of the final result (after summation),
          for input of `str` type, prepend '~' to the input string. '~' must
          be prepended to the *entire string* and not to each bit flag!
  
      Parameters
      ----------
      val : int, str, None
          An integer bit mask or flag, `None`, or a comma- or '+'-separated
          string list of integer bit values. If `val` is a `str` and if
          it is prepended with '~', then the output bit mask will have its
          bits flipped (compared to simple sum of input val).
  
      Returns
      -------
      bitmask : int or None
          Returns and integer bit mask formed from the input bit value
          or `None` if input `val` parameter is `None` or an empty string.
          If input string value was prepended with '~', then returned
          value will have its bits flipped (inverse mask).