code: function isSafeMethod(method, safeMethods) {
      method = method.toUpperCase();
      return (safeMethods || SAFE_METHODS).some(function(safeMethod) {
          return method.toUpperCase() === safeMethod;
      });
  }
docs: Is the given HTTP method (e.g., GET) non-destructive?
  
  @param {string} method HTTP method to test
  @param {string[]} [safeMethods] HTTP methods to consider as "safe"
  @return {boolean}