def _block_name_base(stage, block):
    """Get the convolution name base and batch normalization name base defined by stage and block.

    If there are less than 26 blocks they will be labeled 'a', 'b', 'c' to match the paper and keras
    and beyond 26 blocks they will simply be numbered.
    """
    if block >= 0 and block < 26:
        block = '%c' % (block + 97)  # 97 is the ascii number for lowercase 'a'
    conv_name_base = 'res' + str(stage) + str(block) + '_branch'
    bn_name_base = 'bn' + str(stage) + str(block) + '_branch'

    return conv_name_base, bn_name_base