algebra.subset(a, b)
  
  Returns true if A is a subset of B or A is equal to B (A ⊆ B).
algebra.subset({type: "critical"}, {}) //-> true
algebra.subset({}, {}) //-> true
  
  
    Parameters
      
        
          - a 
{Set}: A set.
 
        
          - b 
{Set}: A set.
 
        
      
   
  
  
  
    Returns
      {Boolean}: 
true if a is a subset of b.