<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _ExtractProxyConfig(product_yaml_key, proxy_config_data):
 """Returns an initialized ProxyConfig using the given proxy_config_data. Args: product_yaml_key: a string indicating the client being loaded. proxy_config_data: a dict containing the contents of proxy_config from the YAML file. Returns: If there is a proxy to configure in proxy_config, this will return a ProxyConfig instance with those settings. Otherwise, it will return None. Raises: A GoogleAdsValueError if one of the required keys specified by _PROXY_KEYS is missing. """

  cafile = proxy_config_data.get('cafile', None)
  disable_certificate_validation = proxy_config_data.get(
      'disable_certificate_validation', False)

  http_proxy = proxy_config_data.get(_HTTP_PROXY_YAML_KEY)
  https_proxy = proxy_config_data.get(_HTTPS_PROXY_YAML_KEY)
  proxy_config = ProxyConfig(
      http_proxy=http_proxy,
      https_proxy=https_proxy,
      cafile=cafile,
      disable_certificate_validation=disable_certificate_validation)

  return proxy_config