code: def _get_activation(self, F, inputs, activation, **kwargs):
          
          func = {'tanh': F.tanh,
                  'relu': F.relu,
                  'sigmoid': F.sigmoid,
                  'softsign': F.softsign}.get(activation)
          if func:
              return func(inputs, **kwargs)
          elif isinstance(activation, string_types):
              return F.Activation(inputs, act_type=activation, **kwargs)
          elif isinstance(activation, LeakyReLU):
              return F.LeakyReLU(inputs, act_type='leaky', slope=activation._alpha, **kwargs)
          return activation(inputs, **kwargs)
docs: Get activation function. Convert if is string