Can't import helper functions from module - "cannot import name ..." error

Question

I have two scripts, a main file and a smaller module storing some helper functions. My main script opens with

from collections import namedtuple

import rospy
import serial
from sensor_msgs.msg import Imu, MagneticField

from quaternions import euler_deg2rad, euler2quat_ZYX

and in quaternions.py, I have

from collections import namedtuple
import numpy as np

def euler_deg2rad(yaw, pitch, roll):
   ....

Attempting to run the main script throws an ImportError: cannot import name 'euler_deg2rad' from 'quaternions'

What's going on here? Is importing namedtuple twice creating a circular dependency? Replacing the 'from' import in the main file with just import quaternions works fine, but I'd rather not import the whole module.