code: def _calc_distance(lon0, lat0, lon1, lat1, u):
      r = _prepare_units(u)
  
      lon0, lat0, lon1, lat1 = map(np.radians, [lon0, lat0, lon1, lat1])
  
      dlon = lon1 - lon0
      dlat = lat1 - lat0
  
      a = (
          np.sin(dlat / 2.0) ** 2
          + np.cos(lat0) * np.cos(lat1) * np.sin(dlon / 2.0) ** 2
      )
  
      c = 2 * np.arcsin(np.sqrt(a))
      return c * r
  
file_path: lets-plot/python-package/lets_plot/geo_data/core.py
imports: from typing import Any
  import numpy
  from .geocoder import Geocoder, ReverseGeocoder, NamesGeocoder
label_desc: Use image node_id 8 for calling a global function with example usage: _calc_distance(lon0, lat0, lon1, lat1, u) and returns: unknown