code: def fromHexString(cls, value, internalFormat=False, prepend=None):
          
          try:
              value = SizedInteger(value, 16).setBitLength(len(value) * 4)
  
          except ValueError:
              raise error.PyAsn1Error('%s.fromHexString() error: %s' % (cls.__name__, sys.exc_info()[1]))
  
          if prepend is not None:
              value = SizedInteger(
                  (SizedInteger(prepend) << len(value)) | value
              ).setBitLength(len(prepend) + len(value))
  
          if not internalFormat:
              value = cls(value)
  
          return value
docs: Create a |ASN.1| object initialized from the hex string.
  
          Parameters
          ----------
          value: :class:`str`
              Text string like 'DEADBEEF'