'Add prefixes foreach namespace referenced by parameter types.'

def getprefixes(self):

    namespaces = []
    for l in (self.params, self.types):
        for (t, r) in l:
            ns = r.namespace()
            if (ns[1] is None):
                continue
            if (ns[1] in namespaces):
                continue
            if (Namespace.xs(ns) or Namespace.xsd(ns)):
                continue
            namespaces.append(ns[1])
            if (t == r):
                continue
            ns = t.namespace()
            if (ns[1] is None):
                continue
            if (ns[1] in namespaces):
                continue
            namespaces.append(ns[1])
    i = 0
    namespaces.sort()
    for u in namespaces:
        p = self.nextprefix()
        ns = (p, u)
        self.prefixes.append(ns)
