fact: Record Matroid : Type := { msort :> finType; msets : {set {set msort}}; wf_msets : [&& set0 \in msets, [forall s1 : {set msort}, forall s2 : {set msort}, ((s1 \subset s2) && (s2 \in msets)) ==> (s1 \in msets)] & [forall s1, forall s2, [&& s1 \in msets, s2 \in msets & #|s1| < #|s2|] ==> [exists x, (x \in s2 :\: s1) && ((x |: s1) \in msets) ]] ] }.
imports: mathcomp(all_ssreflect)