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For a poset p we can simply ask for:

M3 = Posets.DiamondPoset(5)
N5 = Posets.PentagonPoset()

p.has_isomorphic_subposet(M3)
p.has_isomorphic_subposet(N5)

1.st example:

p = Poset( { 0  : [10,11],
             10 : [20,21],
             11 : [20,21],
             20 : [3],
             21 : [3],
             3  : [], })
p.show()

p.has_bottom()
p.has_top()

p.has_isomorphic_subposet(M3)
p.has_isomorphic_subposet(N5)

We obtain:

True
True
False
False

2.nd example:

q = Poset( { 0  : [10,11],
             10 : [20,21],
             11 : [20,21],
             20 : [4],
             21 : [3],
             3  : [4], 
             4  : [], })
q.show()

q.has_bottom()
q.has_top()

q.has_isomorphic_subposet(M3)
q.has_isomorphic_subposet(N5)

This time:

True
True
False
True

3.rd example:

r = Posets.DiamondPoset(6).star_product( Posets.ChainPoset(4) )

r.has_isomorphic_subposet(M3)
r.has_isomorphic_subposet(N5)

and of course we get

True
False