sage: H = MacdonaldPolynomialsH(QQ)
    sage: P = MacdonaldPolynomialsP(QQ)
    sage: m = SFAMonomial(P.base_ring())
    sage: Ht = MacdonaldPolynomialsHt(QQ)
    sage: m(P.one())
    m[]
    sage: Ht(P.one())

    sage: R = QQ['q,t'].fraction_field()
    sage: Sym = sage.combinat.sf.sf.SymmetricFunctions(R)
    sage: H = Sym.macdonald().H();
    sage: P = Sym.macdonald().P();
    sage: m = Sym.monomial();
    sage: Ht = Sym.macdonald().Ht();
    sage: m(P.one())
    sage: Ht(P.one())

    def coercion_graph(self, G = None):
        if G is None:
            G = DiGraph()
        if self not in G.vertices():
            G.add_vertex(self)
            for h in self._introspect_coerce()['_coerce_from_list']:
                coercion_graph(h.domain(), G)
                G.add_edge(h.domain(), self)
        return G

    R = QQ['q,t'].fraction_field()
    R.rename("R")
    Sym = sage.combinat.sf.sf.SymmetricFunctions(R); Sym.rename("Sym")
    p = Sym.p();               p.rename("p")
    s = Sym.schur();           s.rename("s")
    e = Sym.elementary();      e.rename("e")
    m = Sym.monomial();        m.rename("m")
    h = Sym.complete();        h.rename("h")
    H = Sym.macdonald().H();   H.rename("H")
    P = Sym.macdonald().P();   P.rename("P")
    J = Sym.macdonald().J();   J.rename("J")
    S = Sym.macdonald().S();   S.rename("S")
    Ht = Sym.macdonald().Ht(); Ht.rename("Ht")
    m.coerce_map_from(P);
    print Ht.coerce_map_from(P)
    G = coercion_graph(Ht)
    G.show()