code: def parse(s):
          
          if s.find('(') == -1 and s.find('[') != -1:
              return DenseVector.parse(s)
          elif s.find('(') != -1:
              return SparseVector.parse(s)
          else:
              raise ValueError(
                  "Cannot find tokens '[' or '(' from the input string.")
docs: Parse a string representation back into the Vector.
  
          >>> Vectors.parse('[2,1,2 ]')
          DenseVector([2.0, 1.0, 2.0])
          >>> Vectors.parse(' ( 100,  [0],  [2])')
          SparseVector(100, {0: 2.0})