def headers(url, cid)
      override = (cid.nil?) ? nil : {:client_customer_id => cid}
      credentials = @credential_handler.credentials(override)
      headers = {
          'Content-Type' => 'application/x-www-form-urlencoded',
          'Authorization' => @auth_handler.auth_string(credentials),
          'User-Agent' => @credential_handler.generate_user_agent(),
          'clientCustomerId' => credentials[:client_customer_id].to_s,
          'developerToken' => credentials[:developer_token]
      }
      skip_report_header = @config.read('library.skip_report_header')
      unless skip_report_header.nil?
        headers['skipReportHeader'] = skip_report_header.to_s
      end
      skip_report_summary = @config.read('library.skip_report_summary')
      unless skip_report_summary.nil?
        headers['skipReportSummary'] = skip_report_summary.to_s
      end
      skip_column_header = @config.read('library.skip_column_header')
      unless skip_column_header.nil?
        headers['skipColumnHeader'] = skip_column_header.to_s
      end
      include_zero_impressions =
          @config.read('library.include_zero_impressions')
      unless include_zero_impressions.nil?
        headers['includeZeroImpressions'] = include_zero_impressions.to_s
      end
      use_raw_enum_values =
          @config.read('library.use_raw_enum_values')
      unless use_raw_enum_values.nil?
        headers['useRawEnumValues'] = use_raw_enum_values.to_s
      end
      return headers
    end
def headers(url, cid)
      override = (cid.nil?) ? nil : {:client_customer_id => cid}
      credentials = @credential_handler.credentials(override)
      headers = {
          'Content-Type' => 'application/x-www-form-urlencoded',
          'Authorization' => @auth_handler.auth_string(credentials),
          'User-Agent' => @credential_handler.generate_user_agent(),
          'clientCustomerId' => credentials[:client_customer_id].to_s,
          'developerToken' => credentials[:developer_token]
      }
      skip_report_header = @config.read('library.skip_report_header')
      unless skip_report_header.nil?
        headers['skipReportHeader'] = skip_report_header.to_s
      end
      skip_report_summary = @config.read('library.skip_report_summary')
      unless skip_report_summary.nil?
        headers['skipReportSummary'] = skip_report_summary.to_s
      end
      skip_column_header = @config.read('library.skip_column_header')
      unless skip_column_header.nil?
        headers['skipColumnHeader'] = skip_column_header.to_s
      end
      include_zero_impressions =
          @config.read('library.include_zero_impressions')
      unless include_zero_impressions.nil?
        headers['includeZeroImpressions'] = include_zero_impressions.to_s
      end
      use_raw_enum_values =
          @config.read('library.use_raw_enum_values')
      unless use_raw_enum_values.nil?
        headers['useRawEnumValues'] = use_raw_enum_values.to_s
      end
      return headers
    end
Initializes a header handler.

 Args:
  - credential_handler: a header with credential data
  - auth_handler: a header with auth data
  - config: API config

 Returns the headers set for the report request.

 Args:
  - url: URL for the report requests
  - cid: clientCustomerId to use

 Returns:
  - a Hash with HTTP headers.