title: TypeError: __init__() got an unexpected keyword argument 'num_workers'
body: <p>I've just started getting to grips with Nornir, which is a python networking library, i'm hoping someone here may have some experience with it because i've tried all sorts of sites so far with this question and gotten nothing in response. I have created 3 YAML files which are needed to make this library function, config.yaml, hosts.yaml and groups.yaml files in notepad++ and have only have these 3 lines of code to start with in python:</p>
  
  <pre><code>from nornir import InitNornir
  nr = InitNornir(config_file="C:/Users/&lt;REMOVED&gt;/Desktop/config.yaml")
  nr.filter(site="uk").inventory.hosts.keys()
  </code></pre>
  
  <p>I'm getting these errors:</p>
  
  <pre><code>Traceback (most recent call last):
    File "C:/Users/&lt;REMOVED&gt;/PycharmProjects/test_project/nornir_test.py", line 7, in &lt;module&gt;
      nr = InitNornir(
    File "C:\Users\&lt;REMOVED&gt;\PycharmProjects\test_project\venv\lib\site-packages\nornir\init_nornir.py", line 66, in InitNornir
      config = Config.from_dict(**kwargs)
    File "C:\Users\&lt;REMOVED&gt;\PycharmProjects\test_project\venv\lib\site-packages\nornir\core\configuration.py", line 279, in from_dict
      core=CoreConfig(**core or {}),
  TypeError: __init__() got an unexpected keyword argument 'num_workers'
  </code></pre>
  
  <p>My config.yaml file looks like this:</p>
  
  <pre><code>---
  core:
    num_workers: 10
  
  inventory:
    plugin: nornir.plugins.inventory.simple.SimpleInventory
    options:
      host_file: "C:/Users/&lt;REMOVED&gt;/Desktop/hosts.yaml"
      groups_file: "C:/Users/&lt;REMOVED&gt;/Desktop/groups.yaml"
  </code></pre>
  
  <p>I have even tried starting it without the config file:</p>
  
  <pre><code>from nornir import InitNornir
  nr = InitNornir(
      core={"num_workers": 100},
      inventory={
          "plugin": "nornir.plugins.inventory.simple.SimpleInventory",
          "options": {
              "host_file": "inventory/hosts.yaml",
              "group_file": "inventory/groups.yaml"
          }
      }
  )
  </code></pre>
  
  <p>But STILL nothing, this isn't something stupid "Windows thing" is it because quite frankly i'm baffled at the moment.</p>
  
  <p>Any help with this would be much appreciated, go easy i'm just a newbie with Nornir but i'm guessing most will be. I'm just not getting the error because the num_workers key clearly has a value assigned to it and I've tried bypassing the config.yaml file as well to see if it was my yaml file and if i'd set it up wrong but i'm getting the same error either way which makes me think its not the yaml file. Either way i'm stumped to be honest.</p>