reading a list of top statements (helper for top_statement*)
```ebnf
top_statements ::= top_statement*
```
function() {
    let result = [];
    while (this.token !== this.EOF && this.token !== "}") {
      const statement = this.read_top_statement();
      if (statement) {
        if (Array.isArray(statement)) {
          result = result.concat(statement);
        } else {
          result.push(statement);
        }
      }
    }
    return result;
  }