AttributeError: 'Selenium2Library' object has no attribute '_current_browser'

[Anandh1924]

AttributeError: 'Selenium2Library' object has no attribute '_current_browser' on running testcase from travis

@staticmethod
def generate_css_pro():
from selenium.webdriver.common.keys import Keys
selenium2lib = BuiltIn().get_library_instance('Selenium2Library')
driver = selenium2lib._current_browser
print("I am here")
tag = driver.find_element_by_xpath('//div[@Class="left-panel layout-column"]')
driver.execute_script("arguments[0].setAttribute('style', 'height:700px')", tag)
print("checking")
time.sleep(4)

Can any one help on this