Only use for square 2D matrices.
initializer_identity(gain = 1)Multiplicative factor to apply to the identity matrix
Other initializers: 
initializer_constant(),
initializer_glorot_normal(),
initializer_glorot_uniform(),
initializer_he_normal(),
initializer_he_uniform(),
initializer_lecun_normal(),
initializer_lecun_uniform(),
initializer_ones(),
initializer_orthogonal(),
initializer_random_normal(),
initializer_random_uniform(),
initializer_truncated_normal(),
initializer_variance_scaling(),
initializer_zeros()