function concat3d_(tensors, axis) {
    return (0, _concat.concat)(tensors, axis);
}
Concatenates a list of `tf.Tensor3D`s along an axis.
See `concat` for details.

For example, if:
A: shape(2, 1, 3) = | r1, g1, b1 |
                    | r2, g2, b2 |

B: shape(2, 1, 3) = | r3, g3, b3 |
                    | r4, g4, b4 |

C = tf.concat3d([A, B], axis)

if axis = 0:
C: shape(4, 1, 3) = | r1, g1, b1 |
                    | r2, g2, b2 |
                    | r3, g3, b3 |
                    | r4, g4, b4 |

if axis = 1:
C: shape(2, 2, 3) = | r1, g1, b1, r3, g3, b3 |
                    | r2, g2, b2, r4, g4, b4 |

if axis = 2:
C = shape(2, 1, 6) = | r1, g1, b1, r3, g3, b3 |
                     | r2, g2, b2, r4, g4, b4 |

@param tensors A list of`tf.Tensor`s to concatenate.
@param axis The axis to concate along.
@return The concatenated array.