<｜begin▁of▁sentence｜>### Instruction:
As a zoologist, let's consider observing two different animal populations in the wild. One population consists of animals with a distinct edge structure represented by the interactions among them: A interacts with B, B interacts with C, and C interacts with D. The second population involves different animals with their own unique set of interactions: E interacts with F, F interacts with G, and G interacts with H.

Now, utilizing the networkx library in Python, let's explore a fictional scenario where we want to combine these two animal populations into a larger habitat. We aim to use the `__iadd__` function provided by networkx to perform an in-place addition, essentially forming a united habitat that includes all animals and their interactions.
### Response:
from igraph import Graph

# Define two graphs
edges_g1 = [(0, 1), (1, 2), (2, 3)]
g1 = Graph(edges=edges_g1)

edges_g2 = [(4, 5), (5, 6), (6, 7)]
g2 = Graph(edges=edges_g2)

# Perform in-place addition (disjoint union) of g1 and g2
g1 += g2

print(g1)
<|EOT|>
