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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_meshes_fld(step, var):
 """Return scalar field along with coordinates meshes. Only works properly in 2D geometry. Args: step (:class:`~stagpy.stagyydata._Step`):
 a step of a StagyyData instance. var (str):
 scalar field name. Returns: tuple of :class:`numpy.array`: xmesh, ymesh, fld 2D arrays containing respectively the x position, y position, and the value of the requested field. """

    fld = step.fields[var]
    if step.geom.twod_xz:
        xmesh, ymesh = step.geom.x_mesh[:, 0, :], step.geom.z_mesh[:, 0, :]
        fld = fld[:, 0, :, 0]
    elif step.geom.cartesian and step.geom.twod_yz:
        xmesh, ymesh = step.geom.y_mesh[0, :, :], step.geom.z_mesh[0, :, :]
        fld = fld[0, :, :, 0]
    else:  # spherical yz
        xmesh, ymesh = step.geom.x_mesh[0, :, :], step.geom.y_mesh[0, :, :]
        fld = fld[0, :, :, 0]
    return xmesh, ymesh, fld