Project: s41467-024-49339-1 | Function: comparedistances (python)

system: You are an expert Python programmer implementing algorithms from scientific papers.
Complete the masked function based on the algorithm description.
Follow Python best practices and maintain consistent code style.
Return **only** the complete Python function code.

user: Complete this Python function:

**DESCRIPTION:** Calculates nearest neighbor distances between virally labeled Purkinje cell puncta from different cerebellar zones using KDTree spatial indexing. Implements bidirectional nearest neighbor search and computes distance percentiles to quantify spatial proximity of multi-zonal convergence.

**KEY TERMS:** {
  "kdtree1": "spatial index for channel 1 puncta",
  "kdtree2": "spatial index for channel 2 puncta",
  "neighbors_array1": "nearest neighbor distances from ch1 to ch2",
  "neighbors_array2": "nearest neighbor distances from ch2 to ch1",
  "percentileofscore": "distance percentile calculation"
}

**CONTEXT CODE:** import numpy as np
import numpy.random as random
from numpy import genfromtxt
from scipy import stats
from scipy import spatial
from scipy.spatial import distance
from scipy.spatial import KDTree
from scipy.spatial.distance import cdist
from scipy.stats import percentileofscore


def comparedistances(csv1,csv2,sumofdistances):
    """Calculates nearest neighbor distances between virally labeled Purkinje cell puncta from different cerebellar zones using KDTree spatial indexing."""
    raise NotImplementedError("Function has been masked for testing purposes")
        
    
### The above code generates percentiles of distances only across channels for one image in a stack. For data in figure, all the distances across stack positions were concatenated in a separate spreadsheet and the percentiles are measured for each animal.
### The percentiles are then averaged across all animals to get the final distribution. 

### In a separate command line, call the following function and replace csv1 and csv2 with the file paths of the .csv files included in this folder.

### For example:
# csv1 = '/Animal_ID6/Animal_ID6_slice1_ch1_centroid_XYcoordinates_csv1.csv'
# csv2 = '/Animal_ID6/Animal_ID6_slice1_ch2_centroid_XYcoordinates_csv2.csv'
# sumofdistances = 'Distances_across_both_channels_Animal_ID6.csv'
# comparedistances(csv1,csv2,sumofdistances)
 


Complete the function implementation replacing "raise NotImplementedError".