LSTM Cell symbol

def lstm(num_hidden, indata, prev_state, param, seqidx, layeridx, dropout=0., num_hidden_proj=0, is_batchnorm=False,
         gamma=None, beta=None, name=None):
    """LSTM Cell symbol"""
    # dropout input
    if dropout > 0.:
        indata = mx.sym.Dropout(data=indata, p=dropout)

    i2h = mx.sym.FullyConnected(data=indata,
                                weight=param.i2h_weight,
                                bias=param.i2h_bias,
                                num_hidden=num_hidden * 4,
                                name="t%d_l%d_i2h" % (seqidx, layeridx))
    if is_batchnorm:
        if name is not None:
            i2h = batchnorm(net=i2h, gamma=gamma, beta=beta, name="%s_batchnorm" % name)
        else:
            i2h = batchnorm(net=i2h, gamma=gamma, beta=beta)

    h2h = mx.sym.FullyConnected(data=prev_state.h,
                                weight=param.h2h_weight,
                                # bias=param.h2h_bias,
                                no_bias=True,
                                num_hidden=num_hidden * 4,
                                name="t%d_l%d_h2h" % (seqidx, layeridx))

    gates = i2h + h2h
    slice_gates = mx.sym.SliceChannel(gates, num_outputs=4,
                                      name="t%d_l%d_slice" % (seqidx, layeridx))

    Wcidc = mx.sym.broadcast_mul(param.c2i_bias, prev_state.c) + slice_gates[0]
    in_gate = mx.sym.Activation(Wcidc, act_type="sigmoid")

    in_transform = mx.sym.Activation(slice_gates[1], act_type="tanh")

    Wcfdc = mx.sym.broadcast_mul(param.c2f_bias, prev_state.c) + slice_gates[2]
    forget_gate = mx.sym.Activation(Wcfdc, act_type="sigmoid")

    next_c = (forget_gate * prev_state.c) + (in_gate * in_transform)

    Wcoct = mx.sym.broadcast_mul(param.c2o_bias, next_c) + slice_gates[3]
    out_gate = mx.sym.Activation(Wcoct, act_type="sigmoid")

    next_h = out_gate * mx.sym.Activation(next_c, act_type="tanh")

    if num_hidden_proj > 0:
        proj_next_h = mx.sym.FullyConnected(data=next_h,
                                            weight=param.ph2h_weight,
                                            no_bias=True,
                                            num_hidden=num_hidden_proj,
                                            name="t%d_l%d_ph2h" % (seqidx, layeridx))

        return LSTMState(c=next_c, h=proj_next_h)
    else:
        return LSTMState(c=next_c, h=next_h)