Inputs to a layer should be tensors. Got: <keras.layers.

The error message suggests that the input to a Keras layer was not a tensor, which is required.

A tensor is a multi-dimensional array, similar to a matrix. In Keras, tensors are represented using the `tf.Tensor` class from the TensorFlow library.

To fix this error, you should ensure that the input to the layer is a tensor. You can use the `tf.constant` function to create a tensor from a Python list or NumPy array:

import tensorflow as tf

# create a tensor from a Python list
input_data = tf.constant([1, 2, 3, 4])

# create a tensor from a NumPy array
import numpy as np
input_data = tf.constant(np.array([[1, 2], [3, 4]]))

Once you have created a tensor, you can pass it as input to a Keras layer. For example:

from keras.layers import Dense

model = Sequential()
model.add(Dense(64, activation='relu', input_shape=(input_dim,)))

Here, the `Dense` layer takes the tensor `input_data` as input, and specifies the shape of the input tensor using the `input_shape` argument.