def find_variable_assignment(self, name):
        """
        Returns the assignment inst associated with variable "name", None if
        it cannot be found.
        """
        for x in self.find_insts(cls=Assign):
            if x.target.name == name:
                return x
        return None

        Returns the assignment inst associated with variable "name", None if
        it cannot be found.
        
numba/core/ir.py