You are asked to implement the Builder design pattern for rendering simple chunks of code.

Sample use of the builder you are asked to create:

cb = CodeBuilder('Person').add_field('name', '""') \
                          .add_field('age', '0')
print(cb)

The expected output of the above code is:

class Person:
  def __init__(self):
    self.name = ""
    self.age = 0

Please observe the same placement of spaces and indentation.