code: def _calc_angles(self, ut, vt):
      # meteorological convention; follows matplotlib
      return np.pi / 2 - np.arctan2(-vt, -ut)
  
imports: import logging
  import sys
  import param
  import numpy
  import pandas
  from cartopy import crs
  from holoviews.core.data import MultiInterface
  from holoviews.core.util import cartesian_product, get_param_values
  from holoviews.operation import Operation
  from shapely.geometry import Polygon, MultiPolygon
  from shapely.geometry.collection import GeometryCollection
  from ..data import GeoPandasInterface
  from ..element import Image, Shape, Polygons, Path, Points, Contours, RGB, Graph, Nodes, EdgePaths, QuadMesh, VectorField, HexTiles, Labels, Rectangles, Segments, WindBarbs
  from ..util import project_extents, path_to_geom_dicts, polygons_to_geom_dicts, geom_dict_to_array_dict
label_desc: Use image node_id 1 for calling the project_windbarbs obj's underlying member method code with example usage: obj._calc_angles(ut, vt) and returns: unknown