code: def map_coord2pix(ra, dec, x_0, y_0, M):
      
      x, y = M.dot(np.array([ra, dec]))
      return x + x_0, y + y_0
docs: this routines performs a linear transformation between two coordinate systems. Mainly used to transform angular
      into pixel coordinates in an image
      :param ra: ra coordinates
      :param dec: dec coordinates
      :param x_0: pixel value in x-axis of ra,dec = 0,0
      :param y_0: pixel value in y-axis of ra,dec = 0,0
      :param M: 2x2 matrix to transform angular to pixel coordinates
      :return: transformed coordnate systems of input ra and dec