[Kwant] Defining uniaxial strain in specified region of graphene

[shrushti . tapar07]

I want to create the graphene strained superlattice-like structure, having 
uniaxial strain defined at the specified region. Please, someone can suggest to 
me how to define the strained region and interface between unstrained and 
strained graphene regions.  
Thanks in Advance
Shrushti