title: How to solve the ThresholdRule TypeError while using google-cloud-billing-budgets library
body: <p>I'm using <code>google-cloud-billing-budgets</code> to automatically create budgets, but I'm getting errors when I try to create the <em>ThresholdRule</em>.
  My code looks like this.</p>
  <pre><code>    new_thresholde_rule = budgets.ThresholdRule({
          'threshold_percent' : [0.9]
      })
  
      new_budget_details = budgets.Budget({
          'display_name': projectId,
          'amount': new_amount,
          'threshold_rules': new_thresholde_rule,
      })
  
      new_budget = client.create_budget(
          request = {
              'parent': BILLING_ACCOUNT,
              'budget': new_budget_details,
          }
      )
  </code></pre>
  <p>The error is this:</p>
  <pre><code>TypeError: [0.9] has type list, but expected one of: int, long, float
  </code></pre>
  <p>I have been following the <a href="https://googleapis.dev/python/billingbudgets/latest/budgets_v1/types.html#google.cloud.billing.budgets_v1.types.ThresholdRule" rel="nofollow noreferrer">documentation</a>, but it did not give me any hint.</p>