docs: def get_meshes_vec(step, var):
      """Return vector field components along with coordinates meshes.
  
      Only works properly in 2D geometry.
  
      Args:
          step (:class:`~stagpy.stagyydata._Step`): a step of a StagyyData
              instance.
          var (str): vector field name.
      Returns:
          tuple of :class:`numpy.array`: xmesh, ymesh, fldx, fldy
              2D arrays containing respectively the x position, y position, x
              component and y component of the requested vector field.
      """
      if step.geom.twod_xz:
          xmesh, ymesh = step.geom.x_mesh[:, 0, :], step.geom.z_mesh[:, 0, :]
          vec1 = step.fields[var + '1'][:, 0, :, 0]
          vec2 = step.fields[var + '3'][:, 0, :, 0]
      elif step.geom.cartesian and step.geom.twod_yz:
          xmesh, ymesh = step.geom.y_mesh[0, :, :], step.geom.z_mesh[0, :, :]
          vec1 = step.fields[var + '2'][0, :, :, 0]
          vec2 = step.fields[var + '3'][0, :, :, 0]
      else:  # spherical yz
          xmesh, ymesh = step.geom.x_mesh[0, :, :], step.geom.y_mesh[0, :, :]
          pmesh = step.geom.p_mesh[0, :, :]
          vec_phi = step.fields[var + '2'][0, :, :, 0]
          vec_r = step.fields[var + '3'][0, :, :, 0]
          vec1 = vec_r * np.cos(pmesh) - vec_phi * np.sin(pmesh)
          vec2 = vec_phi * np.cos(pmesh) + vec_r * np.sin(pmesh)
      return xmesh, ymesh, vec1, vec2