def get_library_document_file(library_document_id, file_id, file_path=nil)
      response = Echochamber::Request.get_library_document_file(token, library_document_id, file_id)
      unless file_path.nil?
        file = File.new(file_path, 'wb')
        file.write(response)
        file.close
      end
      response
    end
def get_library_document_file(library_document_id, file_id, file_path=nil)
      response = Echochamber::Request.get_library_document_file(token, library_document_id, file_id)
      unless file_path.nil?
        file = File.new(file_path, 'wb')
        file.write(response)
        file.close
      end
      response
    end
Retrieves library document file data

 @param library_document_id (REQUIRED)
 @param file_id [String] (REQUIRED)
 @param file_path [String] File path for saving the document.  If none is given, nothing will be saved to disk.
 @return [String] Raw library document file data