how to filter taxonomy vacobulary using views contextual filters I have taxonomy vocabulary 

parent term1 -
  child term1,
  child term2,
  child term3

parent term2 - 
 child term4,
 child term5,
 child term6


I will be passing view arguments as parent term1. So the output should be (child term1,child term2,child term3).

Please let me know how to achieve this using views contextual filters

Thank you very much for your help!
You can refer Hierarchical Select module, which allows you to create taxonomy structure like your requirement and also allows to filter accordingly your requirements in view.