<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _AddInput(self, variable):
 """ Add one more variable as an input of the block :param variable: variable (or signal as it is also a variable) """

        if isinstance(variable, Variable):
            self.inputs.append(variable)
        else:
            print('Error: ', variable.name, variable,
                  ' given is not a variable')
            raise TypeError