UIView
- 
                  
                  Bind layout element to layout guide. 
- 
                  
                  Entity that represents element in layout time 
- 
                  
                  Internal space for layout subelements 
- 
                  
                  Layout element that maintained this layout entity 
- 
                  
                  Removes layout element from hierarchy 
 UIView Extension Reference
        UIView Extension Reference