<｜begin▁of▁sentence｜>### Instruction:
Given an astrophysics collaborations graph in 'astro-ph.gml', can we apply the LEMON community detection algorithm using predefined seed nodes within the graph to find communities of at least 20 nodes and no more than 50 nodes each? Additionally, can we represent the resulting node clustering in a JSON format?
### Response:
import networkx as nx
from cdlib import algorithms

# Load the Astrophysics collaborations graph
G = nx.read_gml('astro-ph.gml')

# Seed nodes for lemon algorithm
seed_nodes = [1, 3, 7]  # These would be specific to the graph structure and problem domain

# Perform community detection using LEMON
communities = algorithms.lemon(G, seeds=seed_nodes, min_com_size=20, max_com_size=50)

# Get a JSON representation of the community structure
communities_json = communities.to_json()
print(communities_json)
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