List all TensorFlow ops that accept strings

    import tensorflow as tf
    from tensorflow.core.framework import op_def_pb2
    from google.protobuf import text_format
    
    def get_op_types(op):
        for attr in op.attr:
            if attr.type != 'type':
                continue
            return list(attr.allowed_values.list.type)
        return []
    
    # directory where you did "git clone"
    tensorflow_git_base = "/Users/yaroslavvb/tensorflow_main.git"
    ops_file = tensorflow_git_base+"/tensorflow/tensorflow/core/ops/ops.pbtxt"
    ops = op_def_pb2.OpList()
    text_format.Merge(open(ops_file).read(), ops)
    
    for op in ops.op:
        # get templated string types
        if tf.string in get_op_types(op):
            print op.name, op.summary
        for arg in op.input_arg:
            if arg.type == tf.string:
                print op.name, op.summary
                break