def _assert_is_type(name, value, value_type):
 if (not isinstance(value, value_type)):
  if (type(value_type) is tuple):
   types = ', '.join((t.__name__ for t in value_type))
   raise ValueError('{0} must be one of ({1})'.format(name, types))
  else:
   raise ValueError('{0} must be {1}'.format(name, value_type.__name__))

def _assert_is_type ( name , value , value_type ) : if ( not isinstance ( value , value_type ) ) : if ( type ( value_type ) is tuple ) : types = ', ' . join ( ( t . __name__ for t in value_type ) ) raise ValueError ( '{0} must be one of ({1})' . format ( name , types ) ) else : raise ValueError ( '{0} must be {1}' . format ( name , value_type . __name__ ) )
assert that a value must be a given type .