In terms of your code, what are you trying to do with subs? Where is it coming from and what do you expect it to do? These are important questions to work out. Even if you are not sure, you should consider sharing a hypothesis and failed attempts so the process is more constructive.
Here’s an example of how subs can work
>>> from sympy import sin
>>> x = 90
>>> my_expression = sin(x) + 7
>>> my_expression
sin(90) + 7
>>> my_expression.subs(x, 0)
7