title: set_weights for a layer issue
body: <p>I'm getting an error about set_weights but I can not fix it. I've added weight as uniform but it's not accepting it. I'm trying to make an ANN‌ with two hidden layers and a binary output level. the code is:</p>
  
  <pre><code># Importing the libraries
  import numpy as np
  import matplotlib.pyplot as plt
  import pandas as pd
  
  # Importing the dataset
  dataset = pd.read_csv('Churn_Modelling.csv')
  X = dataset.iloc[:, 3: 13].values
  y = dataset.iloc[:, -1].values
  
  #Encoding Categorical data
  from sklearn.preprocessing import LabelEncoder, OneHotEncoder
  from sklearn.compose import ColumnTransformer
  labelencoder_X_1 = LabelEncoder()
  X[:, 1] = labelencoder_X_1.fit_transform(X[:, 1])
  labelencoder_X_2 = LabelEncoder()
  X[:, 2] = labelencoder_X_2.fit_transform(X[:, 2])
  ct = ColumnTransformer([('one_hot_encoder', OneHotEncoder(categories='auto'), [1])],remainder='passthrough')
  onehotencoder = OneHotEncoder(categories=[1])
  X = ct.fit_transform(X)
  X = X[:, 1:]
  
  # Splitting the dataset into the Training set and Test set
  from sklearn.model_selection import train_test_split
  X_train, X_test, y_train, y_test = train_test_split(X, y, test_size=0.2, random_state=0)
  
  # Feature Scaling
  from sklearn.preprocessing import StandardScaler
  sc = StandardScaler()
  X_train = sc.fit_transform(X_train)
  X_test = sc.transform(X_test)
  
  # Part 2 - Kares
  import keras
  from keras.models import Sequential
  from keras.layers import Dense
  
  # Initialising the ANN
  classifier = Sequential()
  
  # Add input layer and first hidden layer
  classifier.add(Dense(units=6, weights='uniform', activation='relu', input_dim=11))
  
  # Second hidden layer
  classifier.add(Dense(units=6, weights='uniform', activation='relu'))
  
  # Output layer
  classifier.add(Dense(units=1, weights='uniform', activation='sigmoid'))
  
  # Compiling the ANN
  classifier.compile(optimizer='adam', loss='binary_crossentropy', metrics=['accuracy'])
  </code></pre>
  
  <p>And the error I'm getting is:</p>
  
  <pre><code>ValueError: You called `set_weights(weights)` on layer "dense_1" with a weight list of length 7, but the layer was expecting 0 weights. Provided weights: uniform...
  </code></pre>
  
  <p>What's the problem?
  Thanks.</p>