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Given the following text description, write Python code to implement the functionality described below step by step
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Description:
 This notebook can be used to see how the functionality to deal with Healpix Tiles can be used. 
More specifically, this notebook shows 
- How to obtain points on the edges of Healpixels and demonstrate that this matches Healpy drawings
- How to draw Healpixels on a basemap plot
Step1:  Demo showing that a healpy mollview plot matches points claimed as boundaries
Step2:  The return of this funciton is a tuple of lon and lat
Step3:  How to get more points?
Step4:  Draw a Healpix in basemap
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Python Code:
from opsimsummary import healpix_boundaries
import numpy as np
import healpy as hp
%matplotlib inline
Explanation: This notebook can be used to see how the functionality to deal with Healpix Tiles can be used. 
More specifically, this notebook shows 
- How to obtain points on the edges of Healpixels and demonstrate that this matches Healpy drawings
- How to draw Healpixels on a basemap plot
End of explanation
ipix  = np.array([11])
lon, lat = healpix_boundaries(ipix, nside=4, units='radians', nest=True, step=2)
Explanation: Demo showing that a healpy mollview plot matches points claimed as boundaries
End of explanation
arr = np.ones(hp.nside2npix(4)) * hp.UNSEEN
arr[ipix] = 1
hp.mollview(arr, nest=True)
hp.projscatter(lat, lon)
Explanation: The return of this funciton is a tuple of lon and lat
End of explanation
lon, lat = healpix_boundaries(ipix, nside=4, units='radians', nest=True, step=3)
arr = np.ones(hp.nside2npix(4)) * hp.UNSEEN
arr[ipix] = 1
hp.mollview(arr, nest=True)
hp.projscatter(lat, lon)
lon
Explanation: How to get more points?
End of explanation
from opsimsummary import HPTileVis, HealpixTiles
hptiles = HealpixTiles(preComputedMap='/Users/rbiswas/data/LSST/OpSimData/healpixelized_MINION_1016_256_64_indexed.db',
                       nside=256)
hptvis = HPTileVis(hptiles, None)
fig, tile_center, _  = hptvis.plotTilePointings((552466), projection='cea', paddingFactors=0.5, ax=None,drawPointings=False
                        ,
                                       **dict(fill=False, color='g', alpha=0.01)
                         )
hp.get_all_neighbours(256,theta=552466, nest=True)
for ipix in hp.get_all_neighbours(256, theta=552466, nest=True):
    _, _, _ = hptvis.plotTilePointings(ipix, tile_centers=tile_center, projection='cea', paddingFactors=0.5, ax=fig.axes[0],drawPointings=False
                        ,
                                       **dict(fill=False, color='g', alpha=0.01)
                         )
fig
Explanation: Draw a Healpix in basemap
End of explanation
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