public LemmaDecl(string name, Term statement, Proof proof) :
     this(name, ContextElem.CreateEmptyContext(), statement, proof)
 {
 }
 public LemmaDecl(string name, IList <Term> statements, Proof proof) :
     this(name, ContextElem.CreateEmptyContext(), statements, proof)
 {
 }
 public LemmaDecl(string name, ContextElem contextElem, Term statement, Proof proof) :
     this(name, contextElem, new List <Term> {
     statement
 }, proof)
 {
 }
 public LemmaDecl(string name, ContextElem contextElem, IList <Term> statements, Proof proof) : base(name)
 {
     ContextElem = contextElem;
     Statements  = statements;
     Proof       = proof;
 }