def __init__(self, agg, keys, npts, errtype, metadata={}):
self.agg = agg<EOL>self.keys = keys<EOL>self.npts = npts<EOL>self.errtype = ErrTypes(errtype, None)<EOL>self.erreq = metadata.get('<STR_LIT>', None)<EOL>self.metadata = metadata or {}<EOL>
@param npts either an int or a tuple (min, max)