def exists?(header = self.class::DEFAULT_REQUEST_HEADER)
      retrieval_keys = self.class::UNIQUE_IDENTIFIERS.reject { |k| @data[k].nil? }
      raise IncompleteResource, "Must set resource #{self.class::UNIQUE_IDENTIFIERS.join(' or ')} before trying to retrieve!" if retrieval_keys.empty?
      retrieval_keys.each do |k|
        results = self.class.find_by(@client, { k => @data[k] }, self.class::BASE_URI, header)
        return true if results.size == 1
      end
      false
    end
def exists?(header = self.class::DEFAULT_REQUEST_HEADER)
      retrieval_keys = self.class::UNIQUE_IDENTIFIERS.reject { |k| @data[k].nil? }
      raise IncompleteResource, "Must set resource #{self.class::UNIQUE_IDENTIFIERS.join(' or ')} before trying to retrieve!" if retrieval_keys.empty?
      retrieval_keys.each do |k|
        results = self.class.find_by(@client, { k => @data[k] }, self.class::BASE_URI, header)
        return true if results.size == 1
      end
      false
    end
Check if a resource exists
 @note one of the UNIQUE_IDENTIFIERS, e.g. name or uri, must be specified in the resource
 @param [Hash] header The header options for the request (key-value pairs)
 @return [Boolean] Whether or not resource exists