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"""Singleton metaclass."""
[docs]class Singleton(type):
"""Implements the Singleton Design Pattern using metaclasses.
References
----------
[1] Mastering Python Design Patterns, Singleton.
"""
_instances = {} # type: ignore
def __call__(cls, *args, **kwargs): # type: ignore
"""Call."""
if cls not in cls._instances:
cls._instances[cls] = super(Singleton, cls).__call__(*args, **kwargs)
return cls._instances[cls]