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import { Parser } from "./index.ts";import { IParser, OnParse, Optional } from "./interfaces.ts";export class MaybeParser<A, B> implements IParser<Optional<A>, Optional<B>> {  constructor(    readonly parent: Parser<A, B>,    readonly description = {      name: "Maybe",      children: [parent],      extras: [],    } as const,  ) {}  parse<C, D>(a: A, onParse: OnParse<Optional<A>, Optional<B>, C, D>): C | D {    if (a == null) {      return onParse.parsed(null);    }    const parser = this;    const parentState = this.parent.enumParsed(a);    if ("error" in parentState) {      const { error } = parentState;
      error.parser = parser;      return onParse.invalid(error);    }    return onParse.parsed(parentState.value);  }}