Python get imported modules from source code returned by inspect.getsource

I'm using inspect.getsource to retrieve the source code of functions. However, since some variables are imported at top level of the module containing the functions, it is not returned by inspect.getsource. For example, if we have

import numpy as np
def sqrt(x):
    return np.sqrt(x)

then inspect.getsource(sqrt) will not return the line import numpy as np. Is it possible to automatically retrieve what np here refers to? The import can also be other forms, such as from some_module import some_func, from some_module import *, import some_module as some_name.

Right now I'm using this function in trace function called by sys.settrace, so the solution can be both static (without running the code) or dynamic (when running the code, such as examining the frames).