fact: Definition ParseProductionSingleton str it (p : parse_of_item G str it) : parse_of_production G str [ it ].
imports: Coq.Lists.List Coq.Arith.PeanoNat Fiat.Common Fiat.Common.UIP Fiat.Parsers.ContextFreeGrammar.Core Fiat.Parsers.ContextFreeGrammar.Equality