title: in pydantic.validators.find_validators TypeError: issubclass() arg 1 must be a class
body: <p>Hello I am reading a JSON with the following format:</p>
  <pre class="lang-json prettyprint-override"><code>{
      &quot;1&quot;: {&quot;id&quot;:1, &quot;type&quot;: &quot;a&quot;},
      2: {&quot;id&quot;:2, &quot;type&quot;: &quot;b&quot;},
      &quot;3&quot;: {&quot;id&quot;:3, &quot;type&quot;: &quot;c&quot;},
      &quot;5&quot;: {&quot;id&quot;:4, &quot;type&quot;: &quot;d&quot;}
  }
  </code></pre>
  <p>As you can see the keys are numbers but are not consecutives.</p>
  <p>So I have the following <code>BaseModel</code> to the nested <code>dict</code>:</p>
  <pre class="lang-py prettyprint-override"><code>@validate_arguments
  class ObjI(BaseModel):
      id: int
      type: str
  </code></pre>
  <p>The question is how can I validate that all items in the <code>dict</code> are <code>ObjI</code> without use of:</p>
  <pre class="lang-py prettyprint-override"><code>objIs = json.load(open(path))
  assert type(objIs) == dict
      for objI in objIs.values():
          assert type(objI) == dict
          ObjI(**pair)
  </code></pre>
  <p>I tried with:</p>
  <pre class="lang-py prettyprint-override"><code>@validate_arguments
  class ObjIs(BaseModel):
      ObjIs:  Dict[Union[str, int], ObjI]
  </code></pre>
  <p>EDIT</p>
  <p>The error validating the previous is:</p>
  <pre class="lang-none prettyprint-override"><code>in pydantic.validators.find_validators TypeError: issubclass() arg 1 must be a class
  </code></pre>
  <p>Is this possible?</p>
  <p>Thanks</p>