Dear researchers,
I have unbalanced panel data for a set of firms for the year that extends from 2000-2019. In 2010 a new standard has been issued, and accordingly, firms started to adopt the standard, but the adoption process is not simultaneous. I mean group of firms adopted in 2010, other groups adopted in 2011, other groups adopted in 2012, and so on. The main variables of interest are growth and leverage.

Kindly note that the adoption of the standards measured as a dummy variable (Event) equal 1 in the years of adoption and zero, otherwise

I have use the below code:
Code:
 
 xtreg Growth i.Event##(c.Leverage c.Age c.Size ) i.Year, fe cluster ( COMPANY)
The reviewer of the paper told me to conduct a parallel trend test. So, I don't know if this test is applicable to the generalised DID with two-way fixed model? if yes, could you please tell me how to do it (i.e., code)?

Thanks very much.