Description

Documentation for Isomap at https://scikit-learn.org/stable/modules/generated/sklearn.manifold.Isomap.html#sklearn.manifold.Isomap says I can provide NearestNeighbors object to .fit function. However it doesn't. It throws the error expecting 2D array.
Looking at the source code, I don't see any checks for the type of X data, just if it's a 2D array.
I'm using approach of NN + Isomap because NearestNeighbors supports callable metrics, unlike Isomap.

Expected Results

No error is thrown.

Actual Results

ValueError: Expected 2D array, got scalar array instead:
array=NearestNeighbors(algorithm='auto', leaf_size=30,
         metric=<function isomap_distance at 0x7fa0638c9488>,
         metric_params=None, n_jobs=None, n_neighbors=5, p=2, radius=1.0).
Reshape your data either using array.reshape(-1, 1) if your data has a single feature or array.reshape(1, -1) if it contains a single sample.

Versions

System:
python: 3.6.7 (default, Oct 22 2018, 11:32:17) [GCC 8.2.0]
executable: /usr/bin/python3
machine: Linux-4.14.79+-x86_64-with-Ubuntu-18.04-bionic

BLAS:
macros: SCIPY_MKL_H=None, HAVE_CBLAS=None
lib_dirs: /usr/local/lib
cblas_libs: mkl_rt, pthread

Python deps:
pip: 19.0.3
setuptools: 40.9.0
sklearn: 0.20.3
numpy: 1.14.6
scipy: 1.1.0
Cython: 0.29.6
pandas: 0.22.0