code: def get_operator(self, op):
          
          if op in self.OPERATORS:
              return self.OPERATORS.get(op)
          try:
              n_args = len(inspect.getargspec(op)[0])
              if n_args != 2:
                  raise TypeError
          except:
              eprint('Error: invalid operator function. Operators must accept two args.')
              raise
          else:
              return op
docs: Assigns function to the operators property of the instance.