grequests

Install the library using pip: `pip install grequests` or `python -m pip install grequests`. Ensure you are running your code with the Python interpreter where `grequests` was installed.

Call `grequests.map()` or `grequests.imap()` on the list of `AsyncRequest` objects to send them and get a list of actual `Response` objects. Then iterate over the results of `map`/`imap` to access response attributes. 
```python
import grequests

urls = [
    'http://httpbin.org/status/200',
    'http://httpbin.org/status/201'
]

rs = (grequests.get(u) for u in urls)
responses = grequests.map(rs) # Send the requests and get Response objects

for response in responses:
    if response:
        print(response.status_code)
        print(response.text)
    else:
        print("Request failed or returned None")
```

Always check if the `response` object is not `None` after `grequests.map()` or `grequests.imap()` returns the results, especially when iterating or accessing attributes.
```python
import grequests

urls = [
    'http://httpbin.org/status/200',
    'http://nonexistent-domain-xyz.com' # This might fail
]

rs = (grequests.get(u) for u in urls)
responses = grequests.map(rs, exception_handler=lambda request, exception: None) # Handle exceptions by returning None

for response in responses:
    if response is not None: # Crucial check for NoneType
        print(f"Status: {response.status_code}")
    else:
        print("Request failed.")
```

Ensure that `gevent.monkey.patch_all()` is called as early as possible in your application's entry point, preferably before any other modules that might use blocking I/O (including `requests` if imported directly before `grequests`).
```python
from gevent import monkey
monkey.patch_all() # Should be at the very top of your script

import grequests
# ... rest of your code
```

Ensure `gevent.monkey.patch_all()` is called at the very beginning of your application. If specific modules are causing issues, you might need to explicitly patch them (e.g., `monkey.patch_all(ssl=True, socket=True, select=True)`). Also, verify that all I/O operations are indeed non-blocking or handled by `gevent`-compatible libraries, and avoid infinite blocking loops in your greenlets without yielding control. For `grequests.map`, increasing the `size` parameter (pool size) can sometimes help by providing more workers.