reading a use statement
```ebnf
trait_use_statement ::= namespace_name (',' namespace_name)* ('{' trait_use_alias '}')?
```
function() {
    // defines use statements
    const node = this.node("traituse");
    this.expect(this.tok.T_USE) && this.next();
    const traits = [this.read_namespace_name()];
    let adaptations = null;
    while (this.token === ",") {
      traits.push(this.next().read_namespace_name());
    }
    if (this.token === "{") {
      adaptations = [];
      // defines alias statements
      while (this.next().token !== this.EOF) {
        if (this.token === "}") break;
        adaptations.push(this.read_trait_use_alias());
        this.expect(";");
      }
      if (this.expect("}")) {
        this.next();
      }
    } else {
      if (this.expect(";")) {
        this.next();
      }
    }
    return node(traits, adaptations);
  }