#MRO - Method Resolution order

class A:
    num = 10

class B(A):
    pass

class C(A):
    num = 1

class D(B,C):
    pass

print(D.mro())

# [<class '__main__.D'>, 
#  <class '__main__.B'>, 
#  <class '__main__.C'>, 
#  <class '__main__.A'>, 
#  <class 'object'>]

# The order of this determined using DFS.

#     A
#    / \
#   /   \
#  B     C
#   \   /
#    \ /
#     D