code: def eqavol(ell: Ellipsoid = None) -> float:
      """computes the radius of the sphere with equal volume as the ellipsoid
  
      Parameters
      ----------
      ell : Ellipsoid, optional
            reference ellipsoid
  
      Returns
      -------
      radius: float
          radius of sphere
      """
      if ell is None:
          ell = Ellipsoid.from_name("wgs84")
  
      f = ell.flattening
  
      return ell.semimajor_axis * (1 - f / 3 - f**2 / 9)
  
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 1 for calling a global function with example usage: eqavol(ell) and returns: unknown