input: Write a python function to extract named entities from a given text using spaCy.
  assert extract_named_entities("Apple is looking at buying U.K. startup for $1 billion") == [('Apple', 'ORG'), ('U.K.', 'GPE'), ('$1 billion', 'MONEY')]
  assert extract_named_entities("Barack Obama was born on August 4, 1961, in Honolulu, Hawaii.") == [('Barack Obama', 'PERSON'), ('August 4, 1961', 'DATE'), ('Honolulu', 'GPE'), ('Hawaii', 'GPE')]
  assert extract_named_entities("Google announced the new Pixel at its event in New York City.") == [('Google', 'ORG'), ('Pixel', 'PRODUCT'), ('New York City', 'GPE')]
output: def extract_named_entities(text):
      import spacy
      nlp = spacy.load("en_core_web_sm")
      doc = nlp(text)
      return [(ent.text, ent.label_) for ent in doc.ents]