code: public boolean isTrue(Configuration configuration) {
          for (Clause clause : this.clauses) {
              if (!clause.isTrue(configuration)) return false;
          }
  
          return true;
      }
docs: Checks if formula evaluates to true.
  <p/>
  Formula evaluates to true iff all its clauses evaluates to true.
  
  @param configuration configuration for which to evaluate
  @return formula evaluations