input: Write a python function to fetch the top 10 cryptocurrencies' names and their prices in USD using the requests library and pandas, and return it as a DataFrame.
  assert fetch_crypto_prices().shape == (10, 2)
  assert 'name' in fetch_crypto_prices().columns
  assert 'price_usd' in fetch_crypto_prices().columns
output: def fetch_crypto_prices():
      import requests
      import pandas as pd
  
      url = "https://api.coingecko.com/api/v3/coins/markets"
      params = {
          'vs_currency': 'usd',
          'order': 'market_cap_desc',
          'per_page': 10,
          'page': 1,
          'sparkline': False
      }
      
      response = requests.get(url, params=params)
      data = response.json()
      
      crypto_data = {
          'name': [coin['name'] for coin in data],
          'price_usd': [coin['current_price'] for coin in data]
      }
      
      df = pd.DataFrame(crypto_data)
      
      return df