code: def parse(s):
          
          start = s.find('[')
          if start == -1:
              raise ValueError("Array should start with '['.")
          end = s.find(']')
          if end == -1:
              raise ValueError("Array should end with ']'.")
          s = s[start + 1: end]
  
          try:
              values = [float(val) for val in s.split(',') if val]
          except ValueError:
              raise ValueError("Unable to parse values from %s" % s)
          return DenseVector(values)
docs: Parse string representation back into the DenseVector.
  
          >>> DenseVector.parse(' [ 0.0,1.0,2.0,  3.0]')
          DenseVector([0.0, 1.0, 2.0, 3.0])