code: def curve(
      lat, ell: Ellipsoid = None, deg: bool = True, method: str = "mean"
  ):
      """computes the arithmetic average of the transverse and meridional
      radii of curvature at a specified latitude point
  
      Parameters
      ----------
      lat : float
          geodetic latitudes (degrees)
      ell : Ellipsoid, optional
            reference ellipsoid
      deg : bool, optional
            degrees input/output  (False: radians in/out)
      method: str, optional
          "mean" or "norm"
  
      Returns
      -------
      radius: float
          radius of sphere
      """
  
      if deg:
          lat = radians(lat)
  
      rho = rcurve.meridian(lat, ell, deg=False)
      nu = rcurve.transverse(lat, ell, deg=False)
  
      if method == "mean":
          return (rho + nu) / 2
      elif method == "norm":
          return sqrt(rho * nu)
      else:
          raise ValueError("method must be mean or norm")
  
file_path: pymap3d/src/pymap3d/rsphere.py
imports: from __future__ import annotations
  from .None import rcurve
  from .ellipsoid import Ellipsoid
  from .mathfun import cos, degrees, log, radians, sin, sqrt
  from .vincenty import vdist
label_desc: Use image node_id 5 for calling a global function with example usage: curve(lat, ell, deg, method) and returns: unknown, sqrt