Hi Vishnu,

A few comments about your code

1) your class declaration is missing the class keyword and the class name has a space (which is forbidden), try something like

class MyTestClass

2) When using the Odoo ORM, inheritance also requires a line after the class declaration such as

_inherit = 'base'

3) While the last line will succeed in changing the behavior of BaseModel.write_header, this is not proper inheritance but rather monkey-patching. The difference is you're changing the behavior of the BaseClass instead of creating a new sub-class with a different behavior. For proper inheritance, re-define the method like

def write_header(self): # Note: keep same method signature
    your_code_here_ideally_not_dividing_by_zero