adding avg pool to resnet50

import tensorflow as tf

import deepchem as dc

from deepchem.models import Sequential

from deepchem.models.tensorgraph.layers import Conv2D, MaxPool2D, Conv2DTranspose, Concat, Feature, Label, BatchNorm

from deepchem.models.tensorgraph.layers import Conv2D, MaxPool2D, AvgPool2D, Conv2DTranspose, Concat, Feature, Label, BatchNorm

from deepchem.models.tensorgraph.layers import SoftMaxCrossEntropy, ReduceMean, SoftMax, ReLU, Add, Flatten, Dense

from deepchem.models import TensorGraph

    id4 = self.identity_block(cb4, 3, [512, 512, 2048])

    id4 = self.identity_block(id4, 3, [512, 512, 2048])

    pool2 = MaxPool2D(ksize=[1, 7, 7, 1], in_layers=[id4])

    pool2 = AvgPool2D(ksize=[1, 7, 7, 1], in_layers=[id4])

    flatten = Flatten(in_layers=[pool2])

    dense = Dense(classes, in_layers=[flatten])