docs: def pitch(ax, ay, az):
      '''Angle of x-axis relative to ground (theta)
  
      Args
      ----
      ax: ndarray
          x-axis acceleration values
      ay: ndarray
          y-axis acceleration values
      az: ndarray
          z-axis acceleration values
  
      Returns
      -------
      pitch: ndarray
          Pitch angle in radians
      '''
      import numpy
      # arctan2 not needed here to cover all quadrants, just for consistency
      return numpy.arctan(ax, numpy.sqrt(ay**2+az**2))